WASHINGTON - Russia released a US Navy veteran who had been detained since April in Kaliningrad, a Russian enclave between Poland and Lithuania, a spokesperson for his family announced Thursday, marking the second time in just over a month that an American has been freed from Russian custody.

Russian officials allowed Mr Taylor Dudley, a 35-year-old US citizen, to cross the Polish border. Mr Dudley had been held for nine months, the spokesperson said, although his case was largely unknown to people outside the US government, his family and advocates.

Mr Dudley was greeted in Poland by an official from the US Embassy in Warsaw and by Mr Bill Richardson, a former New Mexico congressman and governor who specialises in negotiating the freedom of Americans detained overseas.

Mr Dudley was backpacking in Europe and had travelled to Poland to attend a music festival, according to the spokesperson, Mr Jonathan Franks.

He said Mr Dudley “at some point crossed the Russian border” into Kaliningrad. It remained unclear why Mr Dudley had crossed into Russian territory and on what charges he might have been held.

There was no evidence that his plight became linked to that of former US Marine and corporate security consultant Paul Whelan, who was arrested in Moscow in December 2018 and convicted on espionage charges. Mr Whelan, his family and US officials insist those charges are fabricated.

Still, the release was notable given the extremely fraught relations between Washington and Moscow since Russia’s invasion of Ukraine nearly a year ago, and the extreme difficulty the Biden administration has faced in freeing other Americans held in Russia.

It also came less than five weeks after Russia’s release of WNBA star Brittney Griner in a prisoner swap that freed Russian arms dealer Viktor Bout from federal prison. But a US official said that, in this case, the Biden administration had not given Russia anything in exchange for Mr Dudley’s release.

Mr Ned Price, the State Department spokesperson, told reporters at a daily briefing that his ability to comment was limited by a privacy law that an individual must waive to allow the State Department to disclose information about the case.

Mr Richardson said in a statement that he had been working “discreetly” with Mr Dudley’s family for about six months to bring about his release, along with US State Department officials and Mr Ara Abramyan, a businessperson close to President Vladimir Putin of Russia, among others.

“It is significant that despite the current environment between our two countries, the Russian authorities did the right thing by releasing Taylor today,” Mr Richardson said in a statement.

The US official, speaking on the condition of anonymity because of the sensitivity of the matter, credited the work of US officials at embassies in Warsaw and Moscow but said that the administration would not provide further details, out of consideration for the family’s privacy.

US officials had not publicised Mr Dudley’s case or declared him “wrongfully detained,” as they did Ms Griner and continue to do for Mr Whelan.

The circumstances of his travel to Kaliningrad, a vestige of Russian conquest in World War II where Moscow maintains a substantial military presence, are murky. Mr Franks said in his statement that Mr Dudley had travelled to Europe “to backpack and seek inspiration for a potential book he was working on.”

Mr Biden officials have been speaking with Russian officials in a continuing effort to secure Mr Whelan’s freedom, but have made no progress since Ms Griner’s release. Many analysts believe that Russia would only trade Mr Whelan for a captured Russian spy, and experts say the US currently does not have any in its custody.

Mr Whelan’s brother, David, said in an email that before Thursday he had never heard of Mr Dudley, and added that there are “dozens of US citizens in Russian prisons who have been sentenced and are not designated wrongfully detained by the State Department. There’s no reason to think any of them are connected to Paul’s case.”

“Over the past year, our team travelled to Moscow and the region multiple times, liaising with our Russian counterparts and conduits,” Mr Franks said in his statement.

Mr Franks and Mr Richardson also said the effort had been helped by a foundation run by American entrepreneur Steve Menzies and Mr Vitaly Pruss, a New York-based businessperson with ties to Russia. NYTIMES