RIO DE JANEIRO (AFP) - Ethiopian Almaz Ayana smashed one of the longest-held records in athletics here Friday (Aug 12) to win the 10,000m as the Olympic track and field competition got off to an electrifying start.

Ayana, 24, pulled away from the leading pack midway through the 25-lap race at the Olympic stadium and never let up to claim a superb victory in 29min 17.45sec.

Her winning time sliced nearly 14 seconds off the previous world best of 29:31.78 set by Wang Junxia in Beijing in 1993, during the era of notorious Chinese coach Ma Junren.

Vivian Cheruiyot of Kenya took silver in a new national record of 29:32.53 while defending champion Tirunesh Dibaba of Ethiopia won bronze in a personal best 29:42.56.

Dibaba, the 2008 and 2012 Olympic champion, had been bidding to become the first woman in history to win three consecutive golds in an individual athletics event.

But instead it was the 31-year-old's younger compatriot who stole the show with a magnificent performance.

Kenya's Alice Aprot had been the early front-runner, quickly leading a group eight runners that broke away from a giant 37-strong field.

But with 12 laps to go Ayana hit the front, accelerating clear to stretch the leading pack.

Cheruiyot went with Ayana but was always struggling to stay in touch, and the closing laps quickly became a race against the clock and a question of whether Ayana could beat Wang's long-standing world best.

With the stadium roaring her home, Ayana scorched home with a 68sec final lap to claim a remarkable victory.

Ayana's victory comes after a troubled year for Ethiopian distance running after the International Association of Athletics Federations in March placed the country in "critical care" with four other nations over failures in their anti-doping regimes.

Two Ethiopian runners also failed dope tests, with Tokyo Marathon winner Endeshaw Negesse testing positive for meldonium.