Russia's foreign minister told his US counterpart on Saturday that a woman arrested in the United States on accusations she was a Russian agent had been detained on "fabricated charges" and should be released.
Sergei Lavrov made the comments about Maria Butina in a phone call to US Secretary of State Mike Pompeo that was aimed at improving bilateral relations, the Russian Foreign Ministry said in a statement in the wake of the recent summit in Helsinki.
On Wednesday, a US judge ordered Butina jailed until her trial after US prosecutors argued she has ties to Russian intelligence and could flee the United States.
Butina has been accused of working with a high-powered Russian official and two unidentified US citizens, trying to infiltrate a pro-gun rights organisation in the United States and influence the United States' foreign policy toward Russia.
Lavrov said the actions of the American authorities, who arrested Butina "on the basis of fabricated charges", were unacceptable and called for her release as soon as possible.
Lavrov and Pompeo also discussed ways to improve bilateral relations on "equal and mutually beneficial grounds" after the leaders of the two countries, Vladimir Putin and Donald Trump, met in Helsinki on Monday.
They also talked over possible joint efforts aimed at improving the humanitarian situation in Syria as well as the "challenges" of Korean peninsula de-nuclearisation.