The former Tottenham and Manchester United midfielder collapsed on the pitch at the Nature Energy Park stadium in Odense, Denmark's third-largest city.
Footage showed the 34-year-old clutching his chest with both hands in the 65th minute of the game and falling to the ground. He was later seen surrounded by players of both teams as medics tended to him.
The Danish Football Federation said in a post on X that Eriksen is "conscious and feeling well under the circumstances", adding that the game had been abandoned.
Eriksen previously suffered a cardiac arrest and had to be resuscitated on the pitch during a Euro 2020 game against Finland in 2021.
He was later fitted with a special heart-starting device known as an Implantable Cardioverter-Defibrillator.
Morten Boesen, Denmark's team doctor, said in a statement via the federation: "Christian is doing well and walked off the pitch himself.
"As I see it, the pacemaker is responding as it should. He was briefly gone, but regained consciousness very quickly, and we were quickly in contact with him.
"He will now undergo further examinations at the hospital to determine what caused the incident. We are in ongoing contact with him and the doctors at the hospital.
"But Christian is doing well, and he asked me to send his regards to all the players and tell them that he was okay."
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Neither Denmark nor Ukraine qualified for this year's World Cup.
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Emergency crews were called to River Road in Barking at around 11.20pm on Saturday.
They found three men - aged 22, 23 and 28 - with stab wounds. All three were taken to hospital, and the 22-year-old remains there in a critical condition.
The other two were later discharged and taken into custody after being arrested on suspicion of attempted murder.
The 23-year-old became unwell in custody and was returned to hospital, the Metropolitan Police said.
Chief Inspector Mo Mahmood said: "Our thoughts are with the critically injured man and his family at this very difficult time.
"We understand the concern this incident will have caused for the local community and officers continue to work at pace to understand what happened."
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He said it was an "isolated incident" and that police patrols would remain in the area over the coming days.
"We know there were a number of people in and around the area at the time of the incident and are appealing for any witnesses or those with information or mobile phone or dash cam footage to please come forward," he said.
"No detail is too small."
The family of Lindsay and Craig Foreman, who have been detained in Iran since January 2025, are calling for the UK government to exchange Iranian convicted stalker Richard Jan for the pair.
Mr Foreman told Sky News that Iranian authorities had signalled their interest in Jan, who is serving a life sentence and has been dubbed the UK's "worst stalker", and his release could be used to secure their freedom.
On the proposed prisoner swap, Mr Lammy told Sky's Trevor Phillips: "Of course, arrangements can be made of that kind, but the specifics on this would not be right. And I'm not sure from what I've heard that this is… credible".
Mr Lammy, who is also the justice secretary, said he could not go into detail on their case because it would "undermine the discussions that we're having with the Iranians".
Ms Foreman's son, Joe Bennett, said he was hopeful there had been a "shift" in the UK government's approach to his mother and stepfather's case following Mr Lammy's comments.
"The question that we wanted to ask as a family is, if this isn't the solution or a proposed solution, then why not?", he said.
"Anything can be done in theory, but it's been a long time coming where it gets the attention it warrants.
"And the conversation to be had, at least we can either get a proposed path to their release or closure that this isn't a solution."
Richard Ratcliffe, whose wife Nazanin Zaghari-Ratcliffe was jailed in Iran for almost six years, said Mr Lammy's words were encouraging, and a prisoner swap should be on the table.
"It is welcome that David Lammy is making positive noises," he said.
"Of course, he is the secretary of state [for justice], so it is in his gift to review parole board decisions, it's in his gift to discuss with his colleagues and find a way."
He said that Jan's case had been raised as part of discussions to secure his wife's release so it was "not a surprise that he continues to be on the table".
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Sir Jeremy Hunt, who was the foreign secretary while Ms Zaghari-Ratcliffe was imprisoned in Iran, said the UK government should be doing "everything it possibly can" to free the Foremans but urged caution.
"Obviously, what you don't want to do is something that leads to the next person being illegally detained by the Iranians," he said.
"So you have to be careful that you don't reward the kind of absolutely despicable behaviour that we're seeing from Iran, one of the very few governments in the world that will arbitrarily detain an innocent person as a tool of diplomatic leverage."
The couple were travelling through Iran on a motorcycle trip around the world when they were detained by Iranian authorities on espionage charges.
Up to 1,000 people took part in the drill in London's Canary Wharf, including dozens of actors, staging an operation meant to test the emergency response to a marauding terrorist attack.
Counter Terrorism Policing London, who organised the exercise - codenamed Firebird, drew on lessons learned from the Manchester Arena terror attacks in 2019 and deployed new technology, such as drones.
The exercise also provided a sobering reminder of the Docklands IRA bombing in 1996, which killed two and left more than 100 injured.
Metropolitan Police Chief Superintendent Kris Wright, who directed the operation, said it was "the largest exercise of its kind... in modern times".
He said: "It is quite poignant that Canary Wharf, the site of one of the most well-known terror attacks London has ever seen, is now hosting an exercise where we assure ourselves that as that threat has evolved, our response and our ability to combat that threat has evolved with it."
It comes after the threat level was moved to "severe" - meaning an attack is highly likely.
Mr Wright said emergency services would be tested to deal with different types of attack scenarios.
"Whether it be a marauding terror attack with knife, with gun, with fire, whether it be vehicles being used as a weapon, or even some of the more technical threats that we face," he said.
Experiences from real-life events and previous exercises all fed the design of the drill.
One of the measures tested was 10-second triage - the process by which emergency services categorise victims at speed.
"That is a lesson that's come from the tragic events of Manchester Arena," Mr Wright added.
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Local make-up colleges were even recruited to make realistic-looking injuries to treat at the scene.
Mr Wright said: "For me, exercises like this give me an opportunity to test what we already know or where we have seen opportunities to learn, and also to test, those newer capabilities.
"The response that Londoners see from their emergency services and partners to the most catastrophic events is, in my opinion, world-leading.
"But we shouldn't be complacent. We should continue to stretch ourselves and test ourselves, and that's what we do here today."
The airport said the tower - from where air traffic controllers coordinate aircraft - was evacuated at 8.33pm local time.
Flights were paused but the airport later said operations had resumed at 10.15pm after the fire department had given the all clear.
However, it warned passengers to expect delays and disruptions and to contact their airline for an update.
Its arrivals board showed multiple inbound and outbound flights had been delayed and others diverted.
Munich airport is the second-busiest in Germany, after Frankfurt, and one of the busiest in Europe.
Flights were also halted for a short time on 30 May after two pilots in separate planes on the tarmac reported seeing a drone over the airport.
Operations restarted about an hour later after a police helicopter search found nothing.