Jailed Kremlin critic Navalny says he's in harsher solitary cell for six months

(Reuters) - Jailed Russian opposition politician Alexei Navalny said on Wednesday he had been moved to a harsher "cell-type" regime of solitary confinement for the next six months where he would be denied visits.

Navalny, 46, is the highest-profile of the few remaining opposition voices in Russia, having gained followers with repeated investigations purporting to show that the ruling class had enriched itself lavishly at the expense of the state.

"I haven't had any visits for 8 months and yesterday I was told that I’d be transferred to a cell-type facility for the maximum possible term of 6 months," Navalny said via a Twitter feed maintained by his associates.

"No visits are allowed there. This means more than a year without a visit. Even maniacs and serial killers serving life sentences have the right to receive a visit, but I don’t."

There was no immediate comment on his statement from the federal penitentiary service.

Navalny is being held at the maximum-security IK-6 penal colony at Melekhovo, about 250 km (115 miles) east of Moscow, and his supporters say his health has deteriorated dramatically after around a dozen spells in solitary confinement.

Almost 500 medics last month signed an open letter to President Vladimir Putin demanding he be given access to civilian doctors.

Navalny was arrested two years ago as he returned to Russia from Germany, where he had been treated for poisoning with a Soviet-era nerve toxin after what he and some Western nations said was a Russian state assassination attempt. The Kremlin denied involvement.

News outlet The Insider, which operates from outside Russia, quoted his lawyer Vadim Kobzev as saying that Navalny had lost 7 kg (15 lb) in jail and was experiencing stomach pains after being given "huge doses" of antibiotics.

"Putin tried to kill Navalny quickly," Navalny's spokesperson Kira Yarmysh tweeted. "Now he is killing him slowly and torturing him."

A Russian prison supervisor said two weeks ago that Navalny's health was not in danger, while the Kremlin has rejected accusations of any state involvement in his poisoning and cast him as a dangerous extremist.

The lawyer-turned-activist has been sentenced to a combined 11-1/2 years in jail in two separate fraud cases, which he says were trumped up to silence him, and his anti-corruption organisation has been banned as extremist.

The documentary "Navalny" about his poisoning and recovery has been nominated for Best Documentary Film at this year's Oscars.

(Writing by Kevin Liffey; Editing by Andrew Osborn)