Russia's top diplomat is calling on Secretary of State Mike Pompeo Michael (Mike) Richard PompeoTreasury sanctions individuals, groups tied to Russian malign influence activities Navalny released from hospital after suspected poisoning Overnight Defense: Pentagon redirects pandemic funding to defense contractors | US planning for full Afghanistan withdrawal by May | Anti-Trump GOP group puts ads in military papers MORE to free a Russian woman accused of acting as an unregistered foreign agent in the United States.

Russian Foreign Minister Sergey Lavrov said Saturday that Maria Butina had been detained on "fabricated charges" and called for her release as soon as possible, Reuters reported.

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Lavrov made the demand during a phone call with Pompeo aimed at improving relations between the two countries, the Russian Foreign Ministry said, according to Reuters.

According to the outlet, the two diplomats also discussed ways to improve Russia-U.S. relations on “equal and mutually beneficial grounds," including on issues such as Syria and the “challenges” of working toward the denuclearization of the Korean Peninsula.

The State Department in its readout of the call on Sunday did not mention Butina, saying that Pompeo and Lavrov discussed "a broad range of issues, some of which were following up from the meeting between President Trump Donald John TrumpBiden on Trump's refusal to commit to peaceful transfer of power: 'What country are we in?' Romney: 'Unthinkable and unacceptable' to not commit to peaceful transition of power Two Louisville police officers shot amid Breonna Taylor grand jury protests MORE and President Putin."

"Among the topics discussed was the fact that Russia had violated its commitment in southwest Syria. The two also discussed how to implement ideas on counterterrorism process coordination and the mutual goal of establishing business-to-business dialogue between private, non-governmentally controlled entities in each of our two countries. The need for Russia to provide equal diplomatic access to the United States, at a level that is fair and reciprocal, was also discussed," it said.

Butina, a 29-year-old Russian citizen, was arrested last Sunday and charged with "conspiracy to act as an agent of the Russian Federation within the United States without prior notification to the Attorney General," according to the Justice Department (DOJ).

“Butina worked at the direction of a high-level official in the Russian government who was previously a member of the legislature of the Russian Federation and later became a top official at the Russian Central Bank,” the DOJ alleges, adding that her purpose was "infiltrating organizations having influence in American politics, for the purpose of advancing the interests of the Russian Federation."

She is being held in custody as a flight risk after appearing in the U.S. District Court for the District of Columbia on Monday.

Butina's charges come days after Robert Mueller Robert (Bob) MuellerCNN's Toobin warns McCabe is in 'perilous condition' with emboldened Trump CNN anchor rips Trump over Stone while evoking Clinton-Lynch tarmac meeting The Hill's 12:30 Report: New Hampshire fallout MORE's special counsel investigation indicted 12 Russian intelligence officers in the 2016 hacking of the Democratic National Committee.

On Monday, Trump appeared to side with Russia over his own intelligence agencies on the issue of Russia's election interference in 2016, though he later sought to walk back the remarks.

--Morgan Chalfant contributed to this report, which was updated on July 22 at 8:58 a.m.