A man was critically wounded in a stabbing in busy Downtown Brooklyn on Wednesday, police said.

The victim, who cops are still working to identify, got into a fight with a man outside a smoke shop near the corner of Jay St. and Willoughby St. around 8:05 p.m., cops and witnesses said.

“It was a fight between two of them and the third guy got involved,” said the owner of the smoke shop, Organic Life convenience store.

One of the men stabbed the victim in the head and neck, police said.

“Suddenly, he fell down,” said another witness, Mohammed Hossan. “He was face-up bleeding. I couldn’t believe it.”

Medics rushed the man to NewYork-Presbyterian Brooklyn Methodist Hospital, where he was in critical condition late Wednesday night.

“He was bleeding heavily from the head,” Hossan said. “It’s crazy.”

The owner of the smoke shop told the Daily News the men are regulars in his store.

“They come in but they start trouble and I wanted nothing to do with them,” said the man, who did not provide his name.

There were no immediate arrests.