RAF Typhoons deployed guided bombs in a joint operation with the French air force on Saturday night.
The Ministry of Defence (MoD) said several access tunnels were targeted, located in a mountainous area north of the central ancient city of Palmyra.
The operation aimed to "help prevent any attempted resurgence of the Daesh terrorist movement". Daesh is another name for Islamic State, often shortened to ISIS or IS.
The facility had been used by IS, most likely to store weapons and explosives, and the surrounding area was devoid of civilians.
There was no indication of any risk to the local population, and all aircraft involved in the operation returned safely.
In December, the US launched strikes in Syria to "eliminate ISIS fighters, infrastructure, and weapons sites".
The MoD said RAF Typhoon FGR4s, supported by a Voyager refuelling tanker, joined French aircraft in a joint strike on the underground facility.
"Our aircraft used Paveway IV guided bombs to target a number of access tunnels down to the facility; whilst detailed assessment is now underway, initial indications are that the target was engaged successfully," the statement added.
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Defence Secretary John Healey said the operation was designed to "eliminate dangerous terrorists who threaten our way of life".
"This action shows our UK leadership, and determination to stand shoulder to shoulder with our allies, to stamp out any resurgence of Daesh and their dangerous and violent ideologies in the Middle East," he said in a statement.
Western aircraft have been conducting patrols to stop a resurgence of the Islamist militant group that ruled parts of Syria until 2019.
Littler, 18, lost the first set at Alexandra Palace but roared back with seven straight sets to win the coveted title in back-to-back years.
It was the teenager's third final in a row, having lost to Luke Humphries in 2024 when he was just 16 years old.
Littler, nicknamed 'the Nuke', lost just four sets across the whole tournament in an utterly dominant display over the festive period.
Littler, quoting two-time world champion boxer Anthony Joshua, said: "The first time was so nice, I had to do it twice."
The win means the 18-year-old becomes just the fourth back-to-back champion alongside Phil Taylor, Adrian Lewis and Gary Anderson. He is also the first man to retain his Ally Pally title since Anderson a decade ago.
As a player who has lifted the Sid Waddell Trophy twice in just three attempts, he extends his advantage as world number one after making a groundbreaking impact on the sport.
He is also the first winner of the £1m prize pot awarded to the victor.
Van Veen becomes the new world number three, despite falling just short in his quest to follow in the footsteps of countrymen Raymond van Barneveld and Michael van Gerwen by winning the World Championship.
Littler paid tribute to Anthony Joshua, who survived a fatal car crash in Nigeria on Monday. He told Sky Sports Darts: "Everyone knows what happened with Anthony Joshua and his guys and his team, rest in peace to his friends.
"But just like AJ said: 'the first time was so nice, I had to do it twice!'"
He said he started playing better from the second set. "I said to myself, 'give it time, you will find it'. I started off from the left of the oche and moved over to the right. It all came to plan.
"Gian, what a tournament, he can be very happy. Every set he was there and behind me. I had to take my chances."
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Littler reeled off an incredible seven sets on the spin to become a back-to-back champion and keep himself firmly on top of the world.
Van Veen was disappointed that he was unable to give Littler a real game.
"Luke wasn't in the mood to give me any more chances today. He played phenomenal.
"I would have liked to lift up the title, but I would have liked more to give Luke a game, and that's what I didn't do.
"I lost too many legs while I wasn't involved. I missed too many chances. But you know, looking back at this tournament, I'm very proud... getting even to the final."
Amber snow warnings have now been issued for northern Scotland, with heavy snow due overnight and the possibility of temporary blizzard conditions.
Across the rest of the UK, a network of yellow warnings are in place for snow and ice.
While not everyone will see snow, it's likely 1-3cm will fall in places - with the potential of 5-8cm in some locations and widespread ice.
As of Saturday lunchtime, more than 20cm (7.9in) of snow had fallen in northern Scotland, with 37cm (14.5in) in the village of Tomintoul in the Cairngorms.
On Sunday, the Met Office issued a fresh yellow warning for ice along parts of England's North East and East coast.
Existing yellow warning areas have also been extended in Wales and South West England, while Scotland and Northern Ireland are also covered by snow and ice warnings.
Most of the yellow warning areas from Sunday persist into Monday, expiring between 11am and 12 noon.
The exception is a snow and ice warning for the North East and East coast of England, which is in force until the end of Monday.
The Met Office has warned of further scattered sleet and snow showers and icy patches on Monday and overnight into Tuesday morning for South West England and western parts of Wales.
That yellow warning expires at 11am.
The weather is expected to have an impact on transport, with those heading out urged to prepare for longer journey times by road.
Some delays and cancellations to rail and air travel are likely, as are power cuts, according to the Met Office.
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The Met Office said: "Winds should ease somewhat into Sunday, with showers by then most prevalent around coasts. Snow showers should finally begin to ease during Monday morning.
"With temperatures inland likely remaining below freezing through the weekend, thaw of lying snow is not expected."
Meanwhile, the UK Health Security Agency (UKHSA) has issued amber warnings which will remain in place until 10am on 9 January.
The alert has been issued for the East Midlands, West Midlands, North East, North West, South East, South West, East of England, Yorkshire and the Humber, and London.
The UKHSA said it means the weather is "likely" to cause significant impacts across health and social care services, including a "rise in deaths" among those with health conditions or aged 65 or over.
Avon and Somerset Police are searching for Matthew Armstrong and Daniel Washbourne, who both have a history of violent offences, with Armstrong convicted of murder.
A third prisoner, suspected of having absconded at the same time, was arrested in Bristol today.
The men fled from HMP Leyhill in South Gloucestershire between 5pm and 8pm on 1 January.
Police have warned anyone who may spot the prisoners to stay away from them and call 999.
Armstrong, 35, and who has known links to Warwickshire, has been described as white, about 5ft 9ins, with ginger hair and scars on his forehead.
He was last seen wearing a burgundy/orange coat, grey cap, grey tracksuit bottoms with blue on the side, and black boots.
Armstrong was convicted in the late 2000s of a murder that occurred during a robbery in Warwickshire.
Washbourne, 40, and who has known links to Herefordshire, has been described as white, about 5ft 6ins, slim, with brown hair and clean shaven.
He was last seen wearing a cream fleece, blue tracksuit bottoms, blue hat and black trainers.
He has previous convictions for violence and false imprisonment.
Avon and Somerset Police said they were informed about the absconders on Thursday evening as they fled.
The force has shared CCTV footage of what the absconders wore on the day they escaped, as it appealed to the public for information.
Lindsay and Craig Foreman were detained on 3 January 2025 while travelling through Iran for four days on a round-the-world motorbike holiday.
They are accused of espionage, which they both deny.
Speaking at a rally in London to mark one year since the couple's capture, Lindsay's son Joe Bennett told Sky News that while the Foreign Office has been good at communicating with the family, the overall response from the government has been "passive" and that he wants a response from the prime minister.
"There's almost this philosophy to let this judicial system play out, which is of course a complete circus, and the fact that they're both being accused of espionage for the British state and the state that they're being accused of spying for aren't coming out in public defending them, I think is criminal, really."
He said the last year has been "crazy".
"It's gone quick, but it's been the most traumatic long time of our lives. Today is about trying to unite people."
He said his mother is "malnourished" and has been putting on a "brave face".
"She's sleeping on a metal frame. You know, it's horrible conditions. There are rats and vermin everywhere. She's woken up with rats in her bed.
"Day by day has an effect because their body is deteriorating, right? That's the reality of it."
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Also attending the rally was Richard Ratcliffe, husband of Nazanin Zaghari-Ratcliffe, who was held in Iran for more than five years before being released in 2022.
"It brings back tough memories of what we went through, how long it lasted - how you need to keep going. It's nice to be here and reminded of how many people cared for us and care for Lindsay and Craig - and the importance of just keeping going and keeping alive the idea that one day it will be different."
On government efforts to secure Linsday and Craig's release, Mr Ratcliffe said they are not doing enough.
"I think that was true in our case, that will be true in Joe's mum's case, you don't know what they're doing behind closed doors. But as years went on I got very sceptical."
A Foreign Office spokesperson said: "We are deeply concerned by reports that Craig and Lindsay Foreman have been charged with espionage in Iran.
"We continue to raise this case directly with the Iranian authorities.
"The FCDO are providing them with consular assistance and remain in close contact with their family members."