NFL star Damar Hamlin has shown “signs of improvement” since suffering a cardiac arrest during a game on Monday, his team says, but he remains in critical condition.

“Damar remains in the ICU (intensive care unit) in critical condition with signs of improvement noted yesterday and overnight,” the Buffalo Bills said in a social media post.

“He is expected to remain under intensive care as his healthcare team continues to monitor and treat him.”

During the first quarter of the Bills’ penultimate regular season game against the host Cincinnati Bengals, Hamlin got to his feet after making a tackle and then collapsed.

After having his heartbeat restored on the field as stunned players from both teams cried, prayed and hugged, an ambulance took Hamlin to University of Cincinnati Medical Center.

The Bills offered no further details, but Hamlin’s friend and business partner Jordon Rooney said that doctors saw promising readings overnight.

“We all remain optimistic,” Rooney told the Associated Press.

He said he was unable to go into further detail on Hamlin’s status at the request of his family not to provide specifics.

Rooney said Hamlin’s family was staying positive and buoyed by the outpouring of worldwide support the second-year Bills player.

An electronic sign saying 'Pray for Damar 3' stands in front of an NFL team's stadium.
A spokesperson for Hamlin’s family said they were staying positive amid the outpouring of support.((AP Photo/Joshua Bessex))

“They are elated right now,” Rooney said.

“Damar is still their first concern, but for them, they always look at how they can turn a somewhat troubling situation into a good one.

“The bounce back from this, for him and his family, is going to be incredible.”

Players and fans from across the NFL rallied to Hamlin’s support, with vigils held in Cincinnati and outside the Bills’ home stadium.

The shock of what happened also reverberated in Pittsburgh, where the 24-year-old Hamlin grew up and was determined to give back to those in need.

NFL fans in Cincinnati Bengals and Buffalo Bills gear pray next to a cross in front of a hospital with a 'Prayers 4 Damar' sign.
People pray during a vigil for Hamlin outside of University of Cincinnati Medical Center.(AP: Darron Cummings)

Fans, players and NFL owners have been making donations to Hamlin’s Chasing M’s Foundation. Its modest goal of raising $US2,500 ($3,650) for a toy drive exceeded $US6.6 million ($9.6 million) by late Wednesday.

US President Joe Biden, speaking to reporters in Kentucky, said Hamlin’s collapse was not a sign that the NFL has become too dangerous, while noting the inherent risk of a sport with violent collisions on nearly every play.

“I think working like hell on the helmets and the concussion protocols, that all makes a lot of sense,” he said.

“But … it is dangerous. We’ve got to just acknowledge it.”

The Bills’ game against fellow Super Bowl contender the Bengals was postponed on Monday after Hamlin collapsed on the field.

The National Football League, whose regular season concludes on Sunday, has said the Buffalo-Cincinnati game would not resume this week.

NFL rxecutive vice-president of communications Jeff Miller said the conversation about what to do about the game has started and a decision would be made in the coming days.

The game, if played, would have playoff implications for both teams as they are battling with the Kansas City Chiefs for the top seed in the American Football Conference, which comes with a first-round playoff bye.

Reuters/AP

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