Ukrainian pilot Nadia Savchenko, who is held in custody in Russia, has been transferred from a pre-trial detention facility in Voronezh, her lawyer Mark Feygin said.

"Nadia Savchenko has been transferred from the Voronezh pre-trial detention facility number three. This only emerged this morning," he told Interfax on Wednesday.

The lawyer could not say where exactly Savchenko was sent.

Feygin wrote on Twitter: "According to the prison administration, Savchenko was moved on Monday. At present, we do not know her whereabouts. We are waiting for an official statement from the investigators on where Nadia Savchenko is."

Another lawyer of the pilot, Nikolai Polozov, also said that he didn't know where Savchenko was at the moment. "I couldn't find Savchenko in jail. The administration reported that she was moved on September 22, but didn't say where. We are beginning to search for her," he wrote on Twitter.

Meanwhile, it was reported earlier that the Ukrainian pilot could be moved to Moscow to undergo psychological and psychiatric tests under hospital conditions.