New Zealand's Zane Robertson took 13 seconds off his personal best in a national record time in the 10,000m at the Rio Olympics.

New Zealand runner Zane Robertson has repeated his claims that doping is being covered up in Kenya after breaking a 39-year-old national record in the Olympic 10,000m final won by Britain's Mo Farah.

Robertson finished 12th at Rio's Olympic Stadium and bettered Dick Quax's record by more than eight seconds to clock 27min 33.67sec as Farah recovered from a fall to retain his title from London.

Farah was tripped with 16 laps to go and fell to the track but he picked himself up and after a sizzling final lap won in 27:05.17.

IAN WALTON/GETTY IMAGES New Zealand's Zane Robertson (black singlet) runs in the 10,000m final at the Rio Olympics.

But after the race Robertson repeated claims he had made about doping being hidden in Kenya.

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"A lot of top guys are dirty. Names are hidden, positive tests are hidden for bribe money. It's a big problem," he said.

MATT HAZLETT/GETTY IMAGES Zane Robertson repeated his claims that "a lot of top guys are dirty", in reference to alleged drug-taking in Kenyan athletics.

"I can only comment on what I know personally - I wouldn't make stuff up."

He refused to identify athletes because of legal concerns.

Congratulations to Zane Robertson @runninelvis for smashing my NZ record in the 10,000m in Rio. Great effort proud of your performance. — Dick Quax (@DickQuax) August 14, 2016

Robertson, who moved to Kenya when 17 to train and now lives in Ethiopia, believed more countries on the African continent were following Kenya's doping example.

"Surely in every East African country there must be some type of a problem because it's just the mentality there to join the game."

The 26-year-old from Hamilton has been outspoken in his criticism of doping in Kenyan athletics and said he had received evil looks from Kenyan athletes since arriving in the Olympic athletes' village.

But he said none of the three Kenyans in Saturday's race, silver medallist Paul Tanui, Bedan Muchiri and Geoffrey Kamworor, had shown him any animosity before it was run.

Tanui led Farah into the home straight on the final lap but the defending champion kicked clear and he had to settle for silver with Robertson's training partner Tamirat Tola from Ethiopia taking bronze.

I'm now just the second fastest 10,000m runner from Hamilton Boy's High School behind Zane Robertson @runninelvis — Dick Quax (@DickQuax) August 14, 2016

​Robertson told Sky Sport he was "really happy" to have achieved his goal of a personal best, after he lowered his previous mark by 13sec.

- NZN