By Scott Malone

RIO DE JANEIRO (Reuters) - American Ashton Eaton held on to his lead in the Olympic decathlon on Thursday and France's Kevin Mayer leap-frogged Canadian Damian Warner to take second place following a strong pole vault performance.

Eaton, who relies on his blazing running speed to offset normally average throwing events, finished the day's first event, the hurdles, in 13.8 seconds, a stride behind Warner, who lived up to his reputation as the world's fastest decathlon hurdler.

But Eaton, 28, came back to beat 26-year-old Warner in the discus with a season's best throw of 45.59 meters, topping his rival's 44.93m, and he held his lead with a 5.20 meters clearance in the pole vault.

The twice world champion has won two of the 10 events - the long jump and 400m - and finished second to Warner in the 100m and 110m hurdles.

France's Mayer, 24, leapt into second place after a successful 5.4m pole vault, sharing the honor of highest vault of the day with Belgium's Thomas van der Plaetsen. That dropped Warner to third overall.

Grenada's Lindon Victor threw 53.24 to win the discus, more than 3 meters further than nearest rival Keisuke Ushiro of Japan, who managed 49.90.

Neither of those two performed strongly in the earlier events, however, and are placed 14th and 22nd overall respectively.

Eaton dashed away from the discus cage briefly between his second and final throws to congratulate countryman Kerron Clement on his first-place finish in the 400m hurdles.

Brazil's Luiz Alberto de Araujo again drew the most cheers from the sparse crowd in the Olympic Stadium, winning the second hurdles heat in 14.17 and managing a 45.10m discus throw, leaving him seventh overall.

The event concludes later on Thursday with the javelin and 1,500 meters.

(Editing by Ed Osmond)