A small bomb exploded Friday at a campaign rally attended by Prime Minister Costas Karamanlis and tens of thousands of his supporters, but caused no injuries, police said.
The explosive was hidden in a garbage bin about 200 yards (meters) from where Karamanlis was about to campaign for re-election in Sunday's vote, and even closer to some of his supporters, said police spokesman Panayiotis Stathis.
The blast came on the last day of campaigning for the election, which Karamanlis called halfway through his second four-year term, citing the need to reform Greece's rapidly cooling, debt-ridden economy.
A police statement said the bomb damaged two parked motorcycles on a street off a downtown Athens avenue that was full of Karamanlis' supporters. The glass entrance to an apartment building also was smashed.
"It caused minor damage. There are no reports of injuries," Stathis told The Associated Press.
The time bomb exploded shortly after 8 p.m. (1700 GMT), minutes before Karamanlis took to the stage for his address, which went ahead as planned. No group immediately claimed responsibility for the blast, which followed anonymous calls to a national newspaper and a TV station providing a 10-minute warning.
Stathis said the device consisted of explosives in a metal cooking pot, which is the signature bomb used by a small far-left group called Conspiracy Nuclei of Fire.
Last week, police arrested four suspected group members _ all Greeks in their twenties _ who were charged with terrorism and involvement in two Athens bomb attacks on politicians that caused no injury and minor damage.
Attacks by far-left militants and anarchist groups have increased sharply since riots in December, sparked by the fatal police shooting of a teenager in Athens.
As Greece prepares for Sunday's election, Karamanlis' conservative party is trailing the main opposition Socialists by at least 6 percentage points, according to polls released Sept. 18 _ the last date one could be published under Greek law.
Conservative spokesman George Koumoutsakos attributed the attack to "idiotic hotheads."
"They did not change anything, the rally was great," Koumoutsakos told the AP. "As PM Karamanlis said, people behind extreme, violent acts will be arrested because the tangle (of domestic terrorism) has started to unravel after the recent arrests."
In his address, Karamanlis pledged zero tolerance for extremists.
"Enemies of democracy ... will not escape," he said, as supporters cheered and waved party flags.
The 52-year-old Karamanlis became the youngest prime minister in modern Greek history when he swept to power in 2004. He won re-election in 2007, but his government has been undermined over the last year by a series of scandals and a tenuous single-seat majority in the 300-member parliament.
It is unclear however whether Socialist opposition leader George Papandreou, a 57-year-old former foreign minister, will be able to sustain his lead to win enough seats Sunday to form a government and avoid a second round of voting.
Authorities had believed that years of far-left terrorist violence were over after the arrest of several members of the country's deadliest group, November 17, following a botched bombing in 2002.
But that changed, especially after the December riots.
Friday's explosion was the highest-profile attack by domestic militants since a powerful bomb blast outside the Athens Stock Exchange on Sept. 2, that caused extensive damage but no injuries.
A group called Revolutionary Struggle, which in 2007 fired a small anti-tank rocket at the U.S. Embassy in Athens, claimed that blast.
On June 17, militants shot dead a policeman guarding a terror trial witness in central Athens. A little-known group calling itself Sect of Revolutionaries claimed responsibility for that attack.
