Greek police, conducting a massive sweep in Athens, have detained more than 1,000 suspected illegal immigrants.

The immigrants believed to be mostly Albanian have been rounded up in a football stadium from where Greek authorities say most will be deported.

The sweep, described by Greek authorities as the biggest ever, began a little after dawn.

Taking the suspected illegal immigrants by surprise, police began to round them up in public squares, empty buildings and abandoned homes.

The immigrants were then escorted in buses and under armed guard to a football stadium on the outskirts of Athens where officials checked their papers.

Greek television showed the immigrants pouring into the open air stadium with little more than the clothes on their backs. Most appeared to be young Albanian men.

One senior policeman said the round-up had quickly proved that the vast majority were living in Greece without legal residence or work permits.

He said the detainees would be deported by police heading a convoy of buses up to the Greek Albanian border.

Crackdown intensifies

The crackdown is expected to intensify over the coming days.

It follows a controversial government decision to step up security along the frontiers which Greece shares with its impoverished Balkan neighbours in addition to hiring a thousand extra police officers to curb crime.

Nearly one million mostly East European immigrants have poured into Greece, the European Union's only Balkan nation.

Over 500,000 are Albanian. Officials believe that almost half of that number have failed to apply for residence permits, preferring instead to live and work illegally.