"We didn't sleep too much and were closely monitoring the situation," said Carlo Capalbo, PIM's director.

The weather remained clear all day, however, and the waters of the Vltava River, which had risen dramatically in the past week as snow in the mountains melted, stayed within the river's banks.

The day ended up exceeding expectations, both in terms of weather and the number of runners participating in the 21-kilometer (13-mile) event.

A record 4,000 competitors from 35 countries took part in the race, which is a warm-up to the full marathon May 14. The Kenyans dominated in both the men's and women's categories.

Caroline Kwambai set a new women's record of 1 hour, 10 minutes, 8 seconds. Meanwhile, her countryman Stephen Kibiwott cleared the route in 1:1:15.

Kibiwott said a strong wind prevented him from besting the men's record, set by another Kenyan, Joseph Ngeny, in 2004. Kibiwott finished eight seconds shy of the record.

Vladimír Špidla, former Czech prime minister and now European commissioner, finished in 1,823rd place with a time of hours and 3 seconds.

For the first time in the event's history, the PIM organized a corporate relay half-marathon, giving business people the opportunity to compete for their companies in four-member teams.

The team from postal services giant Česká pošta won the race.

The half-marathon and the company relay half-marathon kicked off the running season in the capital.

On May 13, the PIM will stage the 8-kilometer City Run, the 4-kilometer Family Run, the 4-kilometer Eco Run and two in-line skating competitions.

The biggest event, the Prague International Marathon, will take place May 14.