Moscow -- The U.S. embassy in Moscow has accused Russia of preventing a doctor from visiting Paul Whelan in the jail where the former Marine has been held for months on espionage charges that he says are trumped up.
The embassy's Twitter account on Monday wrote that while Whelan was receiving "basic medical care" his condition required more than could be provided in the pre-trial detention center where he is locked up.
"Our petition for a consultation with a visiting doctor was denied," the embassy wrote, saying Whelan's "condition worsened" afterwards.
Whelan's brother, David, on Monday told ABC News that he wasn't willing to identify Paul's medical conditions but said that his brother, 49, had made prison authorities aware he has "medical concerns that are common to men our age."
"For the most part, he has received adequate first aid care: ibuprofen for aches, etc." David Whelan wrote in an email. "But he needs to get a doctor's opinion to get an assessment of risk," he wrote, because he is unable to know whether his conditions might be becoming dangerous.
Whelan is being held in Moscow's Lefortovo prison, a former KGB jail that is known for housing suspected spies and political prisoners. Whelan has been kept there since his arrest in late December, when agents from Russia's domestic intelligence agency, the FSB, detained him in his hotel room while he was visiting Moscow for an American friends' wedding.
Russia has charged him with spying but has not made public any details.
Whelan has denied the charges and during recent court hearings to prolong his detention, he has accused Russia of kidnapping him for political purposes. Whelan's family and his lawyer have alleged he is the victim of a set up by Russia's security services.
Whelan in court last month accused Russian authorities of violating his rights and deliberately isolating him with the intent of pressuring him to make a false confession.
The U.S. State Department has increasingly criticized Russia's treatment of Whelan, demanding it provide evidence against him and accusing Russia of hindering consular access to him. Last week, the U.S. embassy said it had requested Russia's foreign ministry investigate Whelan's "inappropriate treatment".
In response, the deputy head of Russia's Federal Prison Service, Valery Maximenko denied there was any threat to Whelan, telling the Interfax news agency Whelan's "safety was ensured to the full extent."
Lefortovo is one of the most closed jails in Russia. As in other Russian prisons, inmates rely on their relatives for even basic toiletries and it is often hard to receive medicine, and requests for medical check ups are frequently ignored.
Human rights monitors who briefly visited Whelan in January told ABC News then that Whelan's cell was relatively clean and comfortable, but expressed concern that he was prevented from talking with them.
Whelan has British, Irish and Canadian citizenship in addition to American, and Britain has also complained its access has been delayed.
The case remains wrapped in secrecy but Whelan's lawyers say he is accused of receiving a memory card that contained state secrets and which they allege the FSB planted on Whelan by co-opting a long-time Russian friend of his.
Former U.S. intelligence officials have said the case resembles a classic KGB frame up. There has been speculation that Russia may have seized Whelan in the hope of trading him for a Russian held in America.
The speculation was revived on Monday when Russia's deputy foreign minister Sergey Ryabkov called on the U.S. to free a jailed Russian pilot in exchange for an American held in Russia. The pilot, Konstantin Yaroshenko, has been serving a 20-year-sentence in an American jail for drug smuggling since 2011.
"Free Yaroshenko, exchange him for an American or Americans, who are serving their punishment here," Ryabkov told reporters on Monday, saying it could be a "small step" to help start improving relations.
Speculation around a possible swap has previously focused on Maria Butina, the Russian gun rights activist convicted in 2018 by a U.S. court as a foreign agent for attempting to infiltrate American conservative political groups.