Hong Kong retained their Asian Games men's rugby sevens title on Tuesday when they beat South Korea 14-7 in the final in Hangzhou, as hosts China won the women's gold.

After an attritional first half, Hong Kong took the lead right on the siren when Liam Doherty broke two tackles.

He flipped the ball to Cado Lee running off his shoulder and Lee did the rest. Russell Webb converted.

They doubled their advantage seconds into the second half when Doherty was released into space by Max Denmark's quick pass and ran in unopposed to score. Again Webb added two points.

South Korea got a consolation try through Kim Eui-tae but Hong Kong were always in control.

Japan, beaten 12-7 by Hong Kong in a semi-final sudden-death extra-time thriller, came from behind to prevent China winning a shock bronze.

China took a 19-14 lead at the end of the second half to a huge roar from a packed home crowd at the Hangzhou Normal University Athletics Field.

As China kicked off, the siren sounded for full-time, giving Japan one last play.

They made it count with Kippei Taninaka touching down to tie the scores and Yoshihiro Noguchi converting to silence the fans.

But the crowd were cheering again a few minutes later as China held on to pip Japan 22-21 in the women's final, which turned into another nail-biter.

Captain Gu Yaoyao opened the scoring in the first minute and three further touchdowns gave the hosts a seemingly comfortable 22-0 half-time lead.

But a stirring second-half fightback had China on the ropes and only a mad scramble to kick the ball dead behind their own tryline after the siren denied Japan a winning try.

China regained the gold medal they first won in 2014 at Incheon, gaining revenge for losing the final 7-5 to Japan in Jakarta five years ago.

Hong Kong's women won an Asian Games sevens medal for the first time when they held out in the face of wave after wave of Thailand attacking play to prevail 7-5. (AFP)