The Athens first instance prosecutor’s office launched on Monday an investigation into allegations that four suspects arrested for a double bank robbery, two of whom have been linked to an urban guerrilla group, were abused while in police custody.

The probe was launched following media reports and complaints by relatives of the detainees, arrested following two armed bank raids in Velvento, northern Greece.

Public Order Minister Nikos Dendias promised “merciless punishment” if police officers are found to have abused the suspects, aged 20 to 24.

Two of the suspects have been linked to Conspiracy of the Cells of Fire, a group that carried out a series of bloodless bomb attacks.

Speaking to Mega TV on Monday morning, Dendias insisted allegations that the detainees had been tortured would be investigated.

“We will not accept any breach of rights,” he said.

The Public Order Ministry issued a statement on Sunday insisting that the suspects’ injuries were inflicted when they were arrested on Friday after two armed bank robberies and a chase involving a hostage.

Two of the suspects have been linked to the Conspiracy of the Cells of Fire urban guerrilla group.

Dendias also said that the police informed him they doctored the photos of the four suspects so they would be recognizable to the public.

The minister said the police took the unusual step of publishing pictures of the detainees, who appear heavily bruised despite the doctoring of the images, because they wanted to gather more information about possible hideouts.

Anti-terrorism squad officers were searching an apartment in the northern Athens suburb of Maroussi on Monday after reportedly receiving an anonymous tip off.

The prosecutors’ investigation into the possible abuse of the detainees comes after political parties expressed concern on Sunday.

“The torture of detainees is a disgrace for the Greek state,” said SYRIZA. “It is very difficult for even the leadership at the ministry to think this is an isolated incident,” added the opposition party with reference to a recent Guardian report on police abuse.

SYRIZA called for judicial authorities to investigate the matter.

Democratic Left (DIMAR), a junior partner in the three-party coalition, also called for a probe.

“Terrorism is the enemy of society and democracy must confront it decisively,” said DIMAR.

“However, democracy does not exact revenge. An investigation and explanations are needed with regard to the faces that have been deformed due to beatings.”

Police in western Macedonia also issued a statement insisting that only “necessary force” had been used to apprehend and disarm the suspects, who had allegedly carried out two armed robberies and taken a hostage.

The police also said that the alleged robbers had been armed with Kalashnikov assault rifles, a Scorpion submachine gun, handguns and a shotgun.

Police issued a statement on Sunday saying they have matched the fingerprints of one of the suspects with those found at two properties, one in the Athens neighborhood of Kallithea and one in Volos, central Greece, that were used as hideouts for Conspiracy of the Cells of Fire.