Greek police investigate in the Athens suburb of Nea Smyrni after discovering a large weapons cache [AFP]

The Greek anti-terrorist police have arrested at least seven people after discovering guns, grenades and explosives in house searches around Athens.

A police source said the arrests on Saturday, which include a suspected bank robber, were carried out following a police raid on a garage in the district of Nea Smyrni, a few kilometres from Athens, and in other homes in the capital and the neighbouring port of Piraeus.

"A number of detentions have been carried out in the course of extensive investigations by the anti-terrorist department," the police said.

The police uncovered during the raid, three Kalashnikov assault rifles, three semi-automatic guns, seven handguns, four grenades, 50 kilogrammes of industrial-grade ammonium nitrate explosives, and 200 grams of TNT, the police said in a statement.

The police have so far not linked the arrests to any particular group.

Under threat

However, there are some suspicions about a Greek far-left group, called the Revolutionary Sect, which recently boasted of possessing a large arsenal and has so far killed two people and threatened further attacks on police and journalists.

Police had so far failed to crack the Revolutionary Sect, which surfaced in 2009 and earlier this year claimed responsibility for the fatal shooting of a 37-year-old journalist outside his home.

The group in July had sent a Greek newspaper a photo of its purported weaponry, among them three Kalashnikov assault rifles, a semi-automatic handgun and a dozen pistols.

In a seven-page manifesto that accompanied the photo, Revolutionary Sect had threatened media, police and prison officials and claimed to be "at war" with Greek democracy.

Police have also indicated a link to another Greek group, Conspiracy of Fire Nuclei, which specializes in arson and bomb attacks and was behind a parcel bomb campaign against European leaders and embassies uncovered last month when two of its suspected members were arrested.

Three of the men arrested on Saturday are suspected members of Conspiracy of Fire Nuclei, a police source said.

The police are also conducting searches in other Greek cities. A full announcement on the case is expected on Sunday.