Beijing - Six Olympic records, including a first-ever swimming record for a Kenyan, were broken in the evening session of the Olympic swimming competition in the Beijing Water Cube on Thursday.

In the first event Brazilian, Cesar Cielo and Amaury Levaux of France broke the Olympic men's 50m freestyle record within one heat of each other.

The Brazilian swam a 21.47 seconds in the 11th of 13 heats to take 0.44 of Alexander Popov's record that the Russian set in 1992, but Levaux countered just one heat later as he managed a 21.46.

Cielo said it was a great feeling to set an Olympic record. "It was kind of sad it only lasted ten seconds. It's always good to win and swim fast."

An astonishing seven other swimmers managed to stay under Popov's time.

The event was the wildcard event at the Beijing Olympics and there were several participants from countries that would normally not compete in the Olympic swimming competition like the Democratic Republic of Congo, for whom Stany Kempombo Ngangola finished in a time of 35.19.

Antigua's coach Bruce Williams, whose swimmer Kareem Valentine managed a 31.23, said that it was important to allow swimmers of smaller nations the opportunity to compete at this level.

"Kareem normally swims in the open ocean, we do not even have a public swimming pool in our country, so for him to swim here is just terrific."

Britain's women's 400m freestyle Olympic champion Rebecca Adlington won her 800m heat in an Olympic record time of 8:18.06, beating the previous mark of 8:19.67 set by American Brooke Bennett in Sydney eight years ago.

Adlington said that she was surprised with her time. "I did not expect that at all."

Americans Kate Ziegler and Katie Hoff, who were amongst the medal favourites, were surprisingly knocked out with the 10th and 11th fastest time.

In the men's 100m butterfly there was an unlikely Olympic record for American-based Kenyan Jason Dunford, whose time of 51.14, was 0.09 faster than Michael Phelps in Athens.

However, Serbian Milorad Cavic managed a 50.76 in the last heat, just beating Phelps, who also comfortably qualified for the semi- finals.

Zimbabwean Kirsty Coventry, who already has three silver medals from this competition, broke the women's 200m backstroke Olympic record with a time of 2:06.76, beating the 2:07.06 Krisztina Egerszegi of Hungary swam in 1992.

Coventry heads a list of qualifiers for the semi-finals that includes Americans Elizabeth Beisel and Margaret Hoelzer, as well as France's Laure Manaudou.