Imprisoned Russian opposition leader Alexei Navalny is in failing health because of a new suspected poisoning and is back in a punishment cell after a few days in regular confinement, a spokeswoman has said.

Anna Veduta, a Washington DC-based vice president of Mr Navalny’s Anti-Corruption Foundation, told the Associated Press that the 46-year-old fell ill last Friday when he was let out of the punishment cell and put in a conventional cell.

He had lost about 18lb over the past 15 days.

On Monday, Mr Navalny wrote on Twitter that he had been put back in a punishment cell for another 15-day term.

An ambulance was called early on Saturday because of acute stomach pains but Mr Navalny received no diagnosis, one of his lawyers, Vadim Kobzev, wrote on Twitter after visiting him in prison.

“We believe he is slowly being administered low doses of poison” in pills he is given without identification, Ms Veduta said.

A video documentary about Mr Navalny won an Oscar last month.

The documentary portrays his career of fighting official corruption, his near-fatal poisoning with a nerve agent in 2020 that he blames on the Kremlin, his five-month recuperation in Germany and his 2021 return to Moscow, where he was taken into custody.

He was later sentenced to two and a half years in prison and was convicted last year of other charges and given another nine-year term.

Mr Navalny has faced unrelenting pressure from Russian authorities, and has been in and out of isolation in a tiny punishment cell.

He is allowed to write letters and have lawyers visit occasionally.

German government spokesperson Christiane Hoffmann said Berlin took note of reports about Mr Navalny’s worsening health “with great concern”.

She added that Germany wants “the inhuman treatment that he is apparently suffering in prison to be lifted”, and wants Russian authorities to ensure he gets access to medical treatment and is released.

Jailed Russian opposition leader Navalny ‘ill after new suspected poisoning’ - Independent.ie