Kenyan runner Samuel Wanjiru has won the Olympic men's marathon title, pulling away from the pack in the final kilometres to give Kenya its first ever Olympic marathon gold.

The 21-year-old powered through the 42.15km course along Beijing's streets on a sunny Sunday morning, setting an Olympic record of 2 hours, 6 minutes, 32 seconds.

Sunday's run was just the third marathon for Wanjiru, who twice broke the world half-marathon record last year.

Two-time world champion Jaouad Gharib of Morocco won silver in 2:07.16 while Ethiopia's Tsegay Kebede, winner of this year's Paris Marathon, took the bronze in 2:10.00.

Ethiopian Deriba Merga had led the field for much of the race but faded at the end to wind up fourth.

Several of the favourites failed to cope with the sweltering Beijing heat, among them defending Olympic champion Stefano Baldini of Italy.

Baldini fell well behind early on as he failed to find the spark that took him to gold in Athens four years ago

The Italian eventually finished 12th.

World record holder, Ethiopia's Haile Gebrselassie, opted out of the Beijing marathon earlier this year citing concerns about Beijing's notorious air pollution.

But an overnight thunderstorm had cleared the air by Sunday morning, providing a clear blue sky for the final day of the Beijing games.

The race saw some clear leaders pull away from the pack early on, and by the halfway mark, eight were grouped at the front, led by Eritrean Yonas Kifle.

At 30 kilometres the frontrunners had dwindled to three - Wanjiru, Merga and Gharib – while Kenya's Luke Kibet, the reigning world champion, fell back after having stayed with the leaders through the early stages.

Kibet eventually pulled out of the race, saying later he had a stomach problem.

By the final two kilometres Wanjiru had opened up an unassailable 18 second lead, entering the Bird's Nest stadium to a standing ovation from the capacity crowd.

Al Jazeera and agencies