Rome, July 27 (DPA) The first day of the swimming competition at the world championships in Rome saw a flood of world records, as three of the four gold medals on offer were won in world record time.

German Paul Biedermann and Italian local favourite Federica Pellegrini respectively won the men's and women's 400-meter freestyle in world record time, while the Dutch women's 4x100m freestyle relay team took nearly two seconds off their own world record, Sunday.

The other gold medal of the day went to the US 4x100m freestyle relay team, which gave American swimming superstar Michael Phelps a winning start at the championships.

Phelps, who can win six gold medals in Rome, did not swim in the morning heats, but was the first swimmer in the finals.

Phelps, who has won an unprecedented eight gold medals at the Beijing Olympics last year and came to Rome having already won 19 world championship gold medals, touched third in a time of 47.78.

However, the final swimmer for the US, Adrian Nathan, managed to pull past France and Russia on the final leg to give victory to the US in a championship-record time of three minutes, 9.21 seconds.

Russia finished second, while France won the bronze medal.

Phelps said that he regarded winning the relay as the perfect way to end the day. 'You realize that you are strong as a team. We wanted to keep the title in the US. We came out, swam our best and we are pretty pleased about it'

Ryan Lochte caused some laughter from his teammates as he said that he felt under pressure going into his swim. 'I looked at Alain Bernard. He is about seven feet and all I thought: how do I race against this guy?'

In the women's relay the Dutch team was pushed hard by Germany, for whom opening swimmer Britta Steffen set a 100m world record in a time of 52.22.

Steffen said it was often easier to break world records in a relay. 'Sometimes you can swim amazing times because you are a part of a team and that makes a huge difference.'

Lying just ahead of Germany on the final turn, Magdalena Veldhuis managed to edge out Daniela Schreiber on the final metres to give the Dutch gold in a time of 3:31.72.

Germany took silver in 3:31.83, while Australia won the bronze medal in 3:33.01.

In the women's 400-metre freestyle, Pellegrini became the first woman to swim under four minutes when she won gold in a time of 3:59.15 seconds, beating Britain's Joanne Jackson and Rebecca Adlington into second and third place.

Jackson finished in 4:00.