The US soldier accused of leaking hundreds of thousands of secret documents to WikiLeaks is to move to Fort Leavenworth in Kansas Reuters

The US soldier accused of downloading hundreds of thousands of state secrets and passing them to WikiLeaks is to be moved from the military prison where he has been held for the past 10 months after international protests that he is being held in conditions amounting to torture.

US officials quoted by AP said that Bradley Manning is to be moved from the military brig in Quantico marine base in Virginia to Fort Leavenworth in Kansas. He was arrested last year in a US base outside Baghdad where he had been working as an intelligence analyst and has since been charged with passing classified information to an unauthorised party.

The charges relate to the posting by WikiLeaks of a trove of state secrets, including US embassy cables first published by the Guardian in tandem with other newspapers.

In Quantico, Manning has been held in solitary confinement under a "prevention of injury order" which, his lawyer has argued, amounts to an unjustified form of coercion ahead of his court martial. In recent weeks he has been stripped of his clothes at night and left wearing only a smock.

Campaigners who have demanded an end to the mistreatment of Manning in jail are sceptical about the move to Fort Leavenworth. The Democratic congressman Dennis Kucinich, who has raised the case on Capitol Hill, said "nothing the department of defence has done so far with respect to PFC Manning provides any assurance that his basic human and constitutional rights are being protected. Any move does not change the fact that he has been held under conditions which may constitute cruel and unusual punishment in violation of the 8th amendment of the US constitution."

In its Twitter feed, WikiLeaks said there was no guarantee of better treatment for Manning in Fort Leavenworth and that access to the prisoner would still be limited to his lawyer and family.

In the past days the outcry about Manning's conditions has grown. The UN rapporteur on torture, Juan Mendez, criticised the US government for refusing him permission to visit Manning in private.

Many of America's most respected constitutional lawyers signed a joint letter denouncing Manning's treatment as unconstitutional and possibly illegal.

Jeh Johnson, the Pentagon's general counsel, told reporters at a hastily announced briefing at the Pentagon: "Given the length of time he's been in pretrial confinement at Quantico ... and given what the likely period of pretrial confinement in the future ... we reached the judgment this would be the right facility for him."