Russia said Friday that its ties with the United States were still in "crisis" despite a prisoner swap involving US basketball star Brittney Griner and Russian arms dealer Viktor Bout.

Tensions between Moscow and Washington have soared in recent months over a range of issues, peaking after President Vladimir Putin sent troops into pro-Western Ukraine.

"It is probably wrong to draw any hypothetical conclusions that this could be a step towards overcoming the crisis that we currently have in bilateral relations," Kremlin spokesman Dmitry Peskov told the Izvestia newspaper.

Ties "continue to remain in a sad state," he said, adding that talks with US authorities allowed "a Russian citizen, who was basically held captive by the Americans for 14 years... to return to his country".

Dubbed the "Merchant of Death", Bout was released Thursday in a prisoner swap in Abu Dhabi involving WNBA star Griner, 32, who was jailed in Russia for possessing vape cartridges with cannabis oil.

Bout, 55, was accused of arming rebels in some of the world's bloodiest conflicts.

He was arrested in an American sting operation in Thailand in 2008, extradited to the United States and sentenced in 2012 to 25 years in prison.