Dozens of black-clad protesters have clashed with riot police in central Athens, smashing shop windows, throwing petrol bombs and burning cars after an anti-government march, the first since the leftist Syriza party took power a month ago.

Around 450 far-left protesters took to the streets on Thursday in opposition to the newly elected left-right coalition government of Prime Minister Alexis Tsipras, Reuters reported. Tsipras' administration made a deal with European Union (EU) partners last week to extend an aid programme to Athens.

The deal has triggered dissent within Tsipras' own party and accusations by some on the hard left that the government is going back on pre-election promises, including to end a much-hated 240b euro ($268b) EU-International Monetary Fund bailout programme.

After the march, about 50 anti-establishment protesters wearing hoods hurled petrol bombs and stones at police in Athens' central Exarchia district, a Bohemian quarter known as a haunt for artists and left-wing intellectuals.

A small number of shop windows and bus stops were also smashed or damaged during the violence.

The incidents, albeit on a small scale, mark the first public disorder against the government, which was elected on January 25 on a promise to write off a chunk of the country's debt and end painful austerity which has helped push one in four Greeks out of work.