A powerful car bomb blew up outside the Athens stock exchange on Wednesday, slightly wounding one woman, in what Greek police suspect was the latest attack by leftist or anarchist groups.

The Athens bourse opened normally despite suffering extensive damage. Eight vehicles nearby were set ablaze.

Leftist and anarchist groups have staged attacks against business and police targets since December 2008, when the police shooting of a teenager sparked Greece's worst riots in decades.

Police said they suspected one of these groups had planted the bomb, which blew out windows on several floors of the stock exchange and hurled debris hundreds of metres (yards) away.

'All evidence shows it was a terrorist attack,' said Greek police spokesman Panayiotis Stathis, adding anti-terrorist police were gathering evidence from the area, which was cordoned off. 'We have no claim of responsibility yet.'    

An anonymous caller warned a Greek newspaper of the attack, apparently aimed at damaging the building but not people.

Police said the makeshift time-bomb was made up of about 15 kilos of explosive material, planted in a white van on a side street of the exchange. A nearby car dealership, other businesses and four apartments were also damaged.

They said the make-up of the bomb was similar to others planted by the leftist Revolutionary struggle, Greece's most militant group, which emerged in September 2003 after the capture of the November 17 group.

In 2007 it fired a grenade at the US embassy in Athens, hitting its facade, and seriously wounded a police officer outside the Culture Ministry in a 2009 shooting.

Police said a home-made bomb exploded at the same time outside a government building in the northern city of Thessaloniki, causing minor damage but no injuries. It was not immediately clear if the two attacks were connected.

The chairman of the Athens Stock Exchange, Spyros Kapralos, said the damage to the building was substantial but officials worked hard to open for trading.

'Despite the huge material damages caused to the building by today's explosion, both the Athens and the Cyprus stock markets will operate normally,' he said.

The Athens stock exchange opened at 0730 GMT and stocks were trading down by 2.4 per cent. Athens and Nicosia share a trading platform.

Leftist and anarchist guerrilla groups have claimed responsibility for several attacks against businesses, cars and police this year, culminating with the assassination of a policeman in his car in June by the Rebel Sect group.

Imitating the November 17 group, which killed 23 Greeks and foreigners in 27 years but avoided hurting bystanders, Greek guerrilla groups usually strike at night when businesses are closed to avoid alienating the public.-Reuters