Japan's Kosuke Kitajima ruined Brendan Hansen's birthday party when he beat him to win the men's 100 metres breaststroke gold medal at the Athens Olympics on Sunday.

Kitajima won the gold in a time of one minute 00.08 seconds ahead of Hansen, who touched the wall in 1:00.25. Hugues Duboscq of France was third in 1:00.88.

Hansen, celebrating his 23rd birthday, led at the halfway mark from Duboscq but Kitajima glided past him on the last lap.

Although Kitajima is also the world champion, Hansen went into the race as favourite after breaking the Japanese swimmer's world record last month.

At Barcelona last year, the 21-year-old from Tokyo set world records in both the 100 and 200 to give Asia their first male world champion but Hansen took both his records away at the U.S. trials earlier this year.

Now, by winning in Athens, Kitajima provided the region with their first male Olympic champion since Daichi Suzuki won the 100 backstroke in 1988.

Kitajima finished a close fourth in the 100 at the Sydney Olympics as a 17-year-old and was 17th in the 200 but began to make great strides soon after.

He was fourth again in the 100 at the 2001 world championships in Fukuoka but collected his first major medal when he finished third in the 200.

He confirmed his position as the rising name of men's breaststroke when he broke the 200 world record at the 2002 Asian Games in Busan, eclipsing the 10-year-old mark of American Mike Barrowman.

He became the first Asian man to hold a swimming world record since Nobutaka Taguchi held the 100 breaststroke record in 1972.

Kitajima, a student at the Nippon Sport Science University in Tokyo, added the 100 record when he won gold at Barcelona in 2003, flashing home from sixth at the halfway stage.

His 200 world record had fallen to Russia's Dmitri Komornikov just before the world championships but Kitajima snatched it back to win his second title.