A severed pig's head was dumped outside an Islamic studies centre in Athens, in a pre-dawn Islamophobic attack in the heart of the Greek capital.

Unknown vandals spray-painted an obscene slogan against Islam on the pavement outside the Arab-Hellenic Centre, which also functions as a Muslim prayer centre, in the district of Moshato.

Worshippers going to Friday prayers found a Christian cross daubed in red on the centre's door and blue paint splashed on the walls.

Pictures of the defaced building were posted online by the Muslim association of Greece, which ironically described the incident as a "friendly attack".

Police said no arrest was immediately made.

Greece has experienced an increasing number of race-related attacks in recent years, mainly targeting Muslim immigrants and Jews, in concurrence with the political ascent of Neo-Nazi party Golden Dawn.

Earlier this week, a state prosecutor demanded all the party's MPs face trial for offences including allegedly running a criminal organisation.

Prosecutor Isidoros Dogiakos demanded that 70 party members - including leader Nikolaos Michaloliakos and 15 other lawmakers - should appear before a criminal court on a series of charges including the murders of an anti-fascist rapper and Pakistani immigrant.

Golden Dawn spokesman Ilias Kasidiaris described Dogiakos' 700-page report as "laughable" and politically motivated.

"There are 700 pages and not one with any real evidence," he said. "Obviously the government is panicking."

The extreme-right party won 18 seats in the 300-strong Greek parliament after national elections in June 2012, its ascent precipitated by Greece's economic crisis and growing unemployment.

Last year its support peaked at 15%, making it the third-most popular party in Greece.

It came third in the latest local and European elections on an anti-bailout anti-EU ticket and performed strongly at local elections in May.