The brother of American Paul Whelan, who has been detained in Russia since 2018 after being convicted on espionage charges in 2020, says the former U.S. Marine telephoned his parents from Russia early Friday, the first contact in more than a week.

In a statement emailed to media outlets, David Whelan said that his brother said he was transferred to a prison hospital last week for a previously undisclosed treatment. During the call, Paul Whelan said he had been returned to his original prison facility.

Friday's call was the first the family had heard from him since November 23.

"The call at least acts as a 'proof of life' even if nothing else has been explained: When Paul went there, why, why the calls stopped, why the US Embassy had to seek information about his whereabouts and the Russian authorities refused to respond," said David Whelan.

Speaking on background to reporters Friday, a State Department spokesman said they could confirm Paul Whelan spoke to consular officers Friday and that Whelan had been transferred to a prison hospital Thanksgiving Day and returned to the IK-17 penal colony on Friday.

The spokesman also confirmed Whelan was able to call home Friday, and said the Embassy continues to press for timely updates on his condition.

"We're grateful that we were able to establish that contact with him," White House National Security Council spokesman John Kirby told reporters Friday. "We prefer obviously that he not be in a penal colony ... but it was reassuring to be able to hear his voice."

The Biden administration has been trying for months to negotiate the release of Whelan, a former Marine and Michigan corporate executive, as well as American WNBA star Brittney Griner, convicted and jailed earlier this year.

Whelan and Griner "shouldn't have to do one more day in Russia, and we're working very, very hard to see that outcome take place," Kirby said.

The Associated Press, quoting a Russian diplomat, reported this week Russia and the United States have repeatedly been on the verge of an agreement on a prisoner exchange. The diplomat indicated a deal is still possible before the year's end.

Some information for this report was provided by the Associated Press and Reuters.