The trip led by the public order minister and police chief is the first step in taking Athens security nationwide two months before the Games begin.

Public Order Minister George Voulgarakis wants regional police to match the "vigilance and readiness" of forces in the Greek capital.

"The implementation of the (security) plan is starting now," Voulgarakis said in a statement. "We want to activate all procedures to take the country into the Olympic period proper."

Athens will be the first summer Games since the September 11, 2001 attacks and organisers are putting in place the biggest ever Olympic security plan at a cost of one billion euros.

A series of minor bombing attacks last month which the Greek government called "isolated domestic events" raised security concerns for the hosts and for countries planning to send their teams to the Games.

Australia angered Games organisers in May when it issued a travel advisory warning visitors to Athens to be cautious, just days after three bombs exploded in the capital.

Greece will deploy up to 70,000 military, police and coastguard personnel, backed up by air and sea patrols provided by NATO to safeguard athletes, officials and visitors during Games time. More than half the country's security forces will be involved, either directly or indirectly.

Sharing long land borders with Balkan neighbours and seas with Turkey, Greece is also beefing up its coastguard and border force in an effort to stem a growing wave of illegal immigrants and secure its borders ahead of the Games.

Greek officials have met with their counterparts from Bulgaria, Albania and Turkey to seek cooperation in sealing off trafficking routes on both sides of the borders.

Athens has already tightened visa controls, angering northern Greek farmers who rely on seasonal labour from Albania and Bulgaria to harvest fruit. But the government has said it would avoid wholesale closure of frontiers.

In addition to border controls, venue security is on the officials' agenda during their visits this week to the four towns - Volos, Iraklion, Patras and Thessaloniki - which will host preliminaries in the Olympic soccer tournament.