ATHENS Urban guerrillas exploded a makeshift bomb outside Greece's parliament on Saturday evening causing no injuries and minor damage, police said.
The latest in a series of blasts, the explosion took place in the heart of Athens, a well policed area where some of the capital's best hotels and the finance ministry are located.
"This was an unprecedented act of terrorism against the Greek people," government spokesman George Petalotis said.
The explosive device, placed next to a garbage bin at the highly symbolic monument of the unknown soldier outside the parliament building, caused a loud blast that was heard kilometres away.
A warning telephone call to a newspaper preceded the explosion by 10 minutes and police evacuated the area.
The blast followed a bomb attack outside the headquarters of Greece's biggest insurer, National Insurance, on December 27.
Police suspect leftist guerrilla group Fire Conspiracy Cells, which claimed responsibility for the attack against the insurance company, may be behind Saturday's explosion, a police official said.
"Fragments of the explosive device are being gathered and taken to the police lab for investigation," the official said.
"There are first reports of minor damage inside the parliament building, some broken glass. The blast was captured by the security cameras outside the building."
Several leftist and anarchist groups have mounted a series of attacks against police, businesses and public institutions since the police killing of a teenager triggered Greece's worst riots in decades in December 2008.
"The message is simple, democracy cannot be terrorised," Prime Minister George Papandreou, who came to parliament later, told reporters.
Police were also checking video footage from surveillance cameras at the site to determine whether they had taped the perpetrator placing the explosive device. The "evzones," presidential guards at the monument of the unknown soldier, stayed put at their guardposts when the device went off, the police official said.
"I assure you those responsible will be arrested and brought to justice," Civil Protection Minister Michael Chrysochoidis told reporters. "Athens is a safe city."
(Editing by Mark Trevelyan)