MOSCOW (AFP) - Russia's top opposition channel known for its critical coverage of President Vladimir Putin on Tuesday faced the prospect of closure after a major cable operator said it would take the station off the air.

Several providers have over the past days dropped the independent Internet and cable channel Dozhd (TV Rain) from their television packages in a move the station called a state-orchestrated intimidation campaign.

On Monday, the main satellite provider Tricolour TV said it would be dropping the channel from February 10.

Dozhd editor-in-chief Mikhail Zygar said the move threatened the very existence of the channel.

"Tricolour TV is the largest operator," he told AFP.

"Its departure is a turning point. This is a red line which makes conclusively clear that a serious war is being waged against us." The channel, known for its detailed coverage of the pro-EU protests in Ukraine and interviews with Russian opposition leaders, has come under unprecedented pressure over the past few days.

The channel's troubles started last week after it conducted a phone-in poll asking Russians whether Leningrad should have been surrendered during World War II in order to save hundreds of thousands of lives during the siege.

The poll appeared on the eve of the 70th anniversary of the lifting of the siege of Leningrad, one of the darkest pages in Russian history which saw at least 800,000 die of hunger.

Dozhd swiftly apologised and pulled the poll but Mr Putin's spokesman Dmitry Peskov told the station it had "crossed all the limits of what can be tolerated".

Senior lawmakers have called on the general prosecutor's officer to probe the television station over possible extremism.

The state telecoms regulator last week warned the channel it violated legislation that included a law aimed at "immortalising victory of the Soviet people in the Great Patriotic War in 1941-1945".