Two Algerian terror suspects who were deported to their homeland last month have been arrested, imprisoned and charged with terrorist activities, despite being assured by Algerian officials in Britain they would face no criminal proceedings. One of them, known as H, withdrew his appeal against deportation after a British official told the Special Immigration Appeals Commission (Siac) in a statement: "The British government has absolutely no reason to believe that H will be arrested or otherwise detained for a prolonged period of time if deported to Algeria." But his legal advisers and Amnesty International now say they fear he will have to face an unfair trial using evidence obtained by torture. The development casts doubt on the government's argument that assurances from Algeria can be relied on and suspects can be safely deported, even though the country has refused to enter into a memorandum of understanding guaranteeing their human rights.The news of the Algerians' imprisonment and prosecution comes as the extremist Islamist preacher Abu Qatada awaits a Siac ruling tomorrow on his appeal against deportation to Jordan.

The Algerians are understood to be facing trial for "participating in a terrorist network operating abroad".

The second man, Reda Dendani, has been implicated by Mahmoud Meguerba, an intelligence source in the ricin trial, according to information received by Amnesty International. Meguerba, who was not called as a witness because he was considered unreliable, is reported to have been tortured by the DRS, the Algerian military security police.

H and Dendani, formerly known as Q, were detained indefinitely without trial under anti-terrorist legislation and later subjected to virtual house arrest under control orders. In August 2005 they were imprisoned under immigration rules pending deportation.

Their lawyer, Gareth Peirce, said they could no longer bear the strain of indefinite detention and had withdrawn their appeals against deportation orders after assurances that they would not be prosecuted.

Amnesty International last night called on Britain to stop deporting terrorist suspects to Algeria.

Before the London Underground bombings in July 2005, the government accepted that Algeria's human rights record meant that sending suspects back there would breach the European convention on human rights, which bans inhuman or degrading treatment or torture.

But in August 2005 the Home Office started moves to deport 15 Algerians deemed, on the basis of secret intelligence unusable as evidence in British courts, to be a danger to national security.

Britain pledged to hammer out memorandums of understanding with Algeria and the other suspects' homelands, guaranteeing that they would not be tortured or mistreated if returned. There would also be independent monitoring, given the countries' poor human rights records. But Algeria claimed this would infringe its sovereignty.

The Home Office said: "We are satisfied we can deport terrorist suspects to Algeria without breaching the UK's domestic and international human rights obligations."