Russian President Vladimir Putin signed into law on Saturday new measures allowing authorities to list foreign media outlets as "foreign agents" in response to what Moscow says is unacceptable U.S. pressure on Russian media.

The new law has been rushed through both Russian houses of parliament in the last two weeks. It will now allow Moscow to force foreign media to brand news they provide to Russians as the work of "foreign agents" and to disclose their funding sources.

A copy of the law was published on the Russian government's online legislation database on Saturday, saying it entered into force from the day of its publication.

Russia's move against U.S. media is part of the fallout from allegations that Russia interfered in last year's U.S. presidential election in favor of Donald Trump.

U.S. intelligence officials have accused the Kremlin of using Russian media organizations it finances to influence U.S. voters, and Washington has since required Russian state broadcaster RT to register a U.S.-based affiliate company as a "foreign agent".

The Kremlin has repeatedly denied meddling in the election and said the restrictions on Russian broadcasters in the United States are an attack on free speech.

The Kremlin's council for human rights has denounced the bill, saying it was vaguely worded and difficult to reasonably enforce.

"Any foreign media could be labeled a foreign agent quite arbitrarily by the justice ministry of the Russian Federation," the council said in a statement.

Highly criticized by Human Rights Watch and Amnesty International, U.S. and other foreign media will have to present themselves as foreign agents on all paperwork and submit to intensive scrutiny of staffing and financing.

The 2012 law, which had applied only to non-governmental organizations, has now been formally extended.

The Voice of America and Radio Free Europe/Radio Liberty, funded by the U.S. Congress, are the first foreign media to have been warned by Moscow they may need to register under the new classification.