A London-based reporter for Russia's state-owned English-language channel RT quit Friday in protest at its coverage of the Malaysia Airlines crash in Ukraine.

Sara Firth is the second person since March to publicly resign from RT, formerly known as Russia Today, over its coverage of the Ukraine crisis.

"I resigned from RT today. I have huge respect for many in the team, but I'm for the truth," Firth wrote on her Twitter account @Sara__Firth.

The Kremlin-funded channel, which provides a staunchly pro-Russia version of events, told AFP that Firth "has declared that she chooses the truth; apparently we have different definitions of truth".

"We believe that the truth is what our reporters see on the ground, with their own eyes, and not what's printed in the morning London newspapers, channel spokeswoman Anna Belkina said in an email.

She said RT was "not surprised" by Firth's decision to leave as she had spoken of plans to switch jobs.

Firth's resignation followed her outpour of other critical tweets denouncing the "lies" by RT, which had even led some of her followers to wonder whether her account had been hacked.

Firth made the comments after one blogger accused her RT colleague Polly Boiko of "taking money to spread (Russian President Vladimir) Putin's lies" about the Malaysia Airlines flight MH17, which went down in rebel-held eastern Ukraine with 298 people aboard on Thursday.

"What am I spreading?" Boiko shot back.

"Lies hun," Firth then stepped in. "We do work for Putin. We are asked on a daily basis if not to totally ignore then to obscure the truth."

"We're taking a paycheck and for that we have to always obey," she later added.

Firth also changed her Twitter handle from @SaraFirth_RT to disassociate her popular account from the channel.

Her last report out of London, according to the RT website, dates from Tuesday.

Washington has said it was a missile from a rebel-held area that likely shot down the MH17 flight with 298 people aboard. RT's coverage, however, has focussed on Russian claims that Ukraine had deployed surface-to-air missiles in the area, without mentioning reports that these systems were also controlled by the pro-Russian separatists.

RT has been accused of biased reporting, particularly since the beginning of the Ukraine crisis last year.

In March a US-based presenter with RT, Liz Wahl, announced during a live broadcast that she was quitting over the channel's "whitewashing" of Kremlin's actions on the Crimean peninsula.

At the time RT described Wahl's resignation as an act of self-promotion.