Ben Simmons missed 10 free-throws as the top-seeded Philadelphia 76ers somehow conspired to lose Game 5 of their NBA play-offs series against the Atlanta Hawks after leading by 26 points at home.

Trae Young and the Hawks pulled off a comeback for the ages, winning 109-106, to take a 3-2 series lead and move within a victory of the Eastern Conference finals.

Young was fouled on a 3-pointer and hit all three free throws with 1 minute 26 seconds remaining to give Atlanta their first lead of the game which they held on to in amazing 15-2 run to close out proceedings.

Joel Embiid scored 17 of his 37 points in the first quarter and had the Sixers on their way toward a romp with a 26-point lead in the first half.

They still led 87-69 at the end of the third before they collapsed.

"We were up. We had it. We didn't play the way we should be playing," Simmons said.

"We got too comfortable ... this one stings, this one hurts"

Simmons, along with Embiid the cornerstone for Philadelphia, missed free throw after free throw, much as he has for most of the post-season, to speed up Atlanta's comeback.

The Australian finished 4 of 14 from the charity stripe for eight points and nine assists.

The All-Star guard admitted his problem at the free-throw line was mental and understands why coach Doc Rivers pulled him with three-minutes left to play.

"Obviously I've got to knock down free throws. It is what it is. That's coach's decision," Simmons said.

He is 22 for 66 from the line in the post-season.

"When Ben makes them, we get to leave him in," Rivers said.

"When he doesn't, we can't. That's just the way it is."

The Hawks won in Philadelphia for second time in the series and can advance to the conference final for the first time since 2015 with a victory Friday night in Atlanta.

Young, after a tentative start, scored a career play-off high 39 points.

"We keep fighting no matter what the score is. I'm proud of this team," Young said.

Danilo Gallinari (16 points), Lou Williams (15 points) and Young opened the fourth on a huge run against the Sixers' second unit and kept attacking once Rivers was forced to put his starters back in.

Didn't matter though as the big shots kept coming for the Hawks as the Sixers ran cold.

Embiid missed two big free throws down the stretch that effectively ended Philly's hopes, while Seth Curry added a post-season best for him of 36 points.

In the later game, Paul George scored 37 points and grabbed 16 rebounds to lead the LA Clippers to a 119-111 victory over Joe Ingles' Utah Jazz in Game 5 of their Western Conference semifinals series.

Marcus Morris scored 25 points and Reggie Jackson added 22 for the Clippers, who won their third straight game to push the top-seeded Jazz to the brink of elimination.

The Clippers shot 51 per cent from the field without Kawhi Leonard in the lineup.

Bojan Bogandovic scored 32 points - while making nine 3-pointers - to lead Utah.

Six players scored in double figures for the Jazz, including Ingles (12 points, six rebounds and six assists).

Utah and Los Angeles will play Game 6 on Friday in Los Angeles.