An explosive device has been set off outside Greece's parliament building in central Athens.

No injuries were reported after the device exploded around 8pm (18:00 GMT) on Saturday.

Police said there was a warning telephone call to the Eleftherotypia newspaper about 10 minutes before the explosion, but no claim of responsibility.

The blast itself was heard kilometres away. Police said the device was placed next to a garbage bin at the tomb of the unknown soldier outside the parliament building.

Authorities evacuated the heavily-trafficked pedestrian area around the site after the warning call was made. 

Al Jazeera's Nicole Itano, reporting from Athens, said the style of the attack was not an uncommon one in the city, usually meant to be "warnings" from far-left groups.

"Usually these bombs, which are placed outside of government building or banks - often there are warning calls before the bombs go off," she said. 

"The intent really, is to send a warning to the government, to the public, to large business, rather than to cause any sort of human casualties."