Lawmakers in Moscow are seeking to compile a list of US officials accused of violating the rights of Russian citizens following the sentencing of Maria Butina, a gun-rights activist accused of being a foreign agent.

"Under unprecedented pressure and in inhumane prison conditions… the Russian national was forced to plead guilty to things to avoid a heavy jail term, with which the prosecution openly threatened her," the lawmakers said in a proposal seen by Izvestia daily.

The prospect of being included on the 'Butina List' should "sober up" foreign officials who are "used to harassing Russian citizens abroad with impunity."

Butina, an American university graduate, was sentenced on Friday to 18 months in prison and deportation from the US by a federal judge in Washington DC after pleading guilty to conspiring to act as a foreign agent without government registration. The decision came as a shock to Butina's family and defense, who hoped for a time-served sentence.

Russian President Vladimir Putin slammed the sentence as "a travesty of justice" on the part of the US government. "There's nothing they can charge [Butina] with, so to avoid looking ridiculous, they decided to slap her with 18 months in prison," he said.

Butina has already spent nine months in prison – much of it in solitary confinement – which will count towards her sentence. Russian Foreign Minister Sergey Lavrov described her jail conditions as "a kind of torture," pointing out that they were created "to break her will and make her confess to something she likely didn't do.