RUSSIAN President Vladimir Putin ratified new legislation on Saturday allowing foreign-funded media to be classed as "agents," following similar US moves against Russia Today (RT).

The Federation Council, the upper house of the Russian parliament, passed the Bill on Wednesday — just a week after it went through the lower State Duma unanimously.

The new law requires foreign-registered media funded from abroad to meet additional requirements or face suspension.

Authorities can designate those media as foreign agents, which they would have to state in broadcasts, print and on websites.

Last week Russia's Justice Ministry warned the US government-funded Voice of America and Radio Free Europe/Radio Liberty, along with its regional outlets, that they could be designated as foreign agents under the new law.

At least seven other US firms could potentially be affected, along with the Foreign Office-funded BBC World Service.

Former journalist Duma MP Pyotr Tolstoy, who drafted the legislation, said last week the list of targeted organisations could grow depending on the US response, adding that Washington's “campaign looks like it’s going to go on for a long time.

“Every time, Russia is going to take hard response measures,” he said, confirming suspicions that the law is a tit-for-tat answer to US attacks on Russian broadcasters.

RT was forced to register as a foreign agent in the US earlier this month under the Foreign Agents Registration Act passed in 1938 to counter pro-nazi propaganda as the second world war loomed.

The registration, made under the threat of legal action, means RT must state that all its reports are broadcast on behalf of the Russian state. 

Editor-in-chief Margarita Simonyan tweeted: “Between legal action and registration, we have chosen the latter.” 

The week before, Ms Simonyan said RT would challenge the move in court, saying: “This demand is discriminative, it runs counter to the principles of democracy and the freedom of speech.” 

On Tuesday, Google parent company Alphabet CEO Eric Schmidt said the leading internet search engine would "de-rank" articles by RT and RIA Novosti's Sputnik website, making them harder to find.

Speaking at the Halifax International Security Forum in Washington, Mr Schmidt denied the move was censorship but said Google would filter out "weaponised" information.