Part-way through the first quarter, Hamlin took a hard hit during a tackle, stood up and then collapsed to the floor.

He received medical attention for over 30 minutes, with ESPN reporting that he had received CPR.

Players from both NFL teams gathered around Hamlin during the treatment, with many of them kneeling to pray and some openly weeping.

The crowd in Cincinnati remained silent and television coverage broke away from the scene on the field.

ESPN said the 24-year-old Hamlin was provided with oxygen as he left after being placed on a stretcher and that his family, watching the game, joined him in the ambulance.

Reports said Hamlin had been taken to the University of Cincinnati Medical Center, about four miles (six kilometers) away.

After the ambulance left the field, reports initially suggested the game was going to restart following a five minute warm-up.

But once the two team's coaches conferred with referees, players were told to head to the locker room, while the game was announced "temporarily suspended."

The NFL then issued a statement saying that league commissioner Roger Goodell had announced the game had been postponed and gave details of Hamlin's condition.

"Hamlin received immediate medical attention on the field by team and independent medical staff and local paramedics. He was then transported to a local hospital where he is in critical condition," the league said in a statement.

"Our thoughts are with Damar and the Buffalo Bills. We will provide more information as it becomes available," the NFL added.

"The NFL has been in constant communication with the NFL Players Association which is in agreement with postponing the game," the statement concluded.

ESPN analyst Booger McFarland, a former NFL player, had called for the league to abandon the game, during the wait for a decision.

"Nobody is concerned about football right now one... they are concerned about one thing, the health and safety of this young man," he said.

Video footage showed that Hamlin had been hit in the upper chest area.

The NFL, one of the most violent team sports, has been dealing with growing concerns in recent years over concussion injuries for players from hits to the head.

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