ATHENS, Greece (AP) _ An Albanian immigrant armed with hand grenades hijacked a bus Wednesday, demanding ransom and safe passage to Albania. At least six passengers and the driver were held captive, police said.

The hijacking near the border town of Goumenissa was the second hostages-for-ransom incident in northern Greece in less than two months. It comes at a time when officials are under public pressure to crack down on illegal immigrants, especially Albanians, who many Greeks claim are responsible for increased crime.

Thousands of Albanians and other foreigners have been rounded up by police for fingerprinting and document checks. The hostage taker, identified by police as Alexandros Alexandrou, claimed his identity papers were destroyed by authorities.

Police said the Albanian used at least two hand grenades to hijack the bus with about 50 passengers aboard as it was headed from Goumenissa, near the Macedonian border, to the northern port of Salonica. He freed about 45 passengers in the village of Limnotopo, near Salonica.

In late May, another Albanian took eight hostages aboard a public bus and forced the vehicle to cross into Albania. The gunman and a Greek hostage were killed in an Albanian police raid.

An Associated Press photographer following the hijacked bus Wednesday said it halted temporarily on a highway just outside the northern town of Edessa, 40 miles northwest of Salonica.

Heavily armed police tried to negotiate with the hostage-taker, who was demanding nearly $800,000, two automatic weapons and safe passage to Albania.

During the negotiations, an elderly man was set free. After about an hour, the bus was allowed to continue in the direction of the Albanian border.

``I grew up here and went everywhere in Greece ... I want two pistols'' and money, the hostage-taker said by cellular phone to Greece's Skai television. ``If I get these I will let them go.''

Residents of Edessa who lined balconies to watch the bus drive through town shouted ``throw them all out,'' a reference to the hundreds of thousands of illegal Albanian immigrants in Greece.

Albanians make up the majority of the estimated 650,000 immigrants living in Greece.