LONDON (AFP) - Usain Bolt said he had sympathy for his friend Mo Farah following the furore surrounding doping allegations against Alberto Salazar, coach of the Briton.

"I've come through the ranks with Mo, so I've seen the work that he's put in," said the Jamaican sprint king on Thursday on the eve of the Anniversary Games Diamond League meeting in London.

"I'm sorry for Mo because every day I hear he's in the papers and they're trying to tear him down," Bolt added.

"I think he's worked so hard to get where he is for somebody's mistake to be causing him problems.

"I just hope that he doesn't take it too seriously and it doesn't make him stress out."

Bolt added that he supported Farah's decision to stand by Salazar.

"When you have confidence in your coach, you know who he is as a person," he said.

"Of course you're going to want to support him as an athlete. If he believes in his coach, I believe in him."

British track star Farah, the reigning Olympic and world champion over both the 5,000m and 10,000m, runs in the 3000m on Friday.

Farah has faced intense media scrutiny after allegations that Salazar administered testosterone to American distance runner Galen Rupp in 2002 when Rupp - a training partner of Farah - was only 16, and encouraged misuse of prescription drugs.

There is no suggestion, however, that Farah has violated anti-doping rules, although he came under pressure after it emerged he missed two drug tests in the lead-up to the London 2012 Olympics.