The New York Knicks produced another stunning comeback to win the second game of their NBA Conference play-off semi-final against the Boston Celtics.

Jalen Brunson made two free throws with 12.7 seconds remaining to give New York a 91-90 lead, before Mikal Bridges knocked the ball away to deny Boston a last-gasp chance.

Josh Hart had a game-high 23 points for New York, who trailed by 20 points in the third quarter and by 16 in the fourth in Boston.

The Knicks lead the reigning NBA champions 2-0 in the best-of-seven series after finishing 10 wins behind their opponents in the regular season.

"I got up there, heard the noise and then I just tried to block everything out. And then I made two," said Brunson - who finished the night with 17 points and a game-high seven assists - on his decisive foul shots.

Karl-Anthony Towns finished with 21 points and 17 rebounds for the Knicks, while Bridges scored all of his 14 points in the fourth quarter.

After coming back from 20 points down in an overtime win in game one, New York did not take the lead in game two until the last two minutes.

"We started slowly, got in a big hole, dug our way out and then guys made a lot of tough plays," said Knicks coach Tom Thibodeau.

"[Our players] were at their best when their best was needed down the stretch."

Derrick White and Jaylen Brown each scored 20 points for the Celtics, who will travel to New York for game three on Saturday.

"They made the necessary plays to win," Boston coach Joe Mazzulla said of the Knicks.

"We put ourselves in position to do that and we just didn't make the plays."

Meanwhile, the Oklahoma City Thunder levelled their semi-final with a 149-106 home blowout win against the Denver Nuggets.

After losing on a three-pointer in the closing seconds of game one, Oklahoma City scored 45 points in the first quarter and tied the NBA play-off record for the most points in a half with 87.

MVP favourite Shai Gilgeous-Alexander led the game with 34 points before watching the fourth from the bench.

"We knew what was at stake tonight," Gilgeous-Alexander said. "We came out desperate."

"I didn't really look at tonight as a response as much as I looked at tonight as just us being who we are, and that's how we've been all season," Oklahoma City coach Mark Daigneault said.

After his 42-point performance in game one, Denver's Nikola Jokic tallied just 17 points and eight rebounds in game two before fouling out in the third quarter.

"We got punked," Denver interim coach David Adelman said.

"They came out with the right intensity and we didn't. We aren't just going to flush this. We have to play better and we know that."