Updated

MOSCOW -- Russian prosecutors are investigating how an independent television station covered December's massive opposition rallies -- with an eye on whether the U.S. or other foreign powers funded the broadcasts, the channel and the lawmaker pursuing the probe said Thursday.

The investigation of the Dozhd station follows a management shakeup at Russia's top independent radio station. The moves signal that the government, which already controls much of Russian media, is increasingly nervous that the two independent media outlets will serve as platforms for opponents of Russian Prime Minister Vladimir Putin.

The rallies in Moscow drew tens of thousands of people angry over December's fraud-tainted parliamentary election, which was won by United Russia, Putin's party. Putin has accused the U.S. of instigating the protests, which have challenged his bid to reclaim the presidency in March's election.

Dozhd's head Nataliya Sindeyeva posted a copy of the prosecutors' letter, which says the probe is conducted on a request by Robert Shlegel, a lawmaker with Putin's party. Shlegel asked the prosecutors to unveil "sources of the financing" of the rallies' coverage.

Shlegel told Dozhd in an phone interview Thursday that he wants to find out "where these activities were financed from -- Russian sources, foreign, or maybe American funds." He said he requested the probe because the privately owned station acted like "a media sponsor and part organizer of these events."

The channel said its lawyers are working to respond to the prosecutors' request.

Dozhd, which has been broadcasting online and through cable and satellite networks since 2010, has become a household name for smart journalism thanks to its extensive coverage of protests and opposition politicians.

Staffed by some of Russia's most prominent journalists, Dozhd is popular among urbanites who shun government propaganda on nationwide TV stations, which are all controlled by the state. It was the only television station to offer full live coverage of protest rallies in December and January.

Authorities previously had stayed away from intervening into the activities of independent media outlets because their coverage and existence helped deflect foreign criticism of Russia's shrinking media freedoms and provided a safety valve for public discontent.

But that reticence appears to be going away.

On Tuesday, the editor of Russia's leading independent radio station, Ekho Moskvy, said its management was being changed in an effort to restrict on-air criticism of the government ahead of the March 4 presidential election.

The media arm of state-controlled natural gas giant Gazprom, which holds two-thirds of the shares, is tightening its hold over the board of directors, editor Alexei Venediktov said.

Gazprom Media took the action after Putin last month accused the station of serving the foreign policy interests of the United States and "pouring diarrhea" on him all day.