A Russian freelance journalist who claims she went undercover as a pro-government Internet troll says she is suing her former employer in a bid to expose the workings of the Kremlin's online army.

"This propaganda on the Internet is very dangerous," Lyudmila Savchuk, 34, told AFP on Tuesday. "It has to be brought to light."

Savchuk has lodged a case against her mysterious former employer, The Agency for Internet Studies, in Saint Petersburg where she says she and colleagues spent their days praising President Vladimir Putin and slamming his enemies online.

She is claiming the outfit hired employees without putting them through the books and said she had not been paid in full.

"But our main aim is to attract the attention of society to this shameful phenomenon," said Savchuk, who is a single mother of two.

She said she hoped to "shut down this troll factory and fight propaganda as a whole".

"I fear for the youth who are working there and are spreading this infection."

Tensions with the West over Ukraine and the takeover of Crimea have increasingly polarised Russian society, with most Russians supportive of Putin but a minority in sharp disagreement.

For a monthly salary of 40,000 to 50,000 rubles ($750-$940 at the current rate) Savchuk bombarded website comment pages with eulogies of the Kremlin strongman and slammed Ukrainian "Fascists."

Unmasked after two months in the job, Savchuk was sacked after she published articles under a pseudonym in local newspapers denouncing the "propaganda factory".

A court in Saint Petersburg on Monday postponed the case to June 23 after no-one showed up to represent Savchuk's former employer.

'Tons of insults from trolls'

Authorities have ratcheted up its propaganda campaign as the crisis over Ukraine has sent tensions with the West soaring to their highest level since the Cold War.

The West and Ukraine accuse Russia of sending its troops to fight in its ex-Soviet neighbour but Putin flatly denies the claim and Russia's government media has done all it can to deflect the accusations.

Savchuk and several dozen like-minded people formed a group in a bid to fight the Kremlin propagandists who they say are fanning hatred in society.

"There are no famous opposition activists among us yet but we have just started our movement," she said.

Savchuk said she had been harassed by pro-Kremlin trolls since breaking cover.

"I am receiving tons of insults from trolls every day.

"I try to not take it to heart although that is not easy."

A lawyer who frequently represents the interests of Kremlin critics vowed to help her fight the pro-Kremlin propagandists.

"We are pleased that the activities of this organisation are becoming visible and we are going to fight against it in court," said Savchuk's lawyer Ivan Pavlov.

"But trolls do not like light and can't exist when there is transparency."