Police in Greece have ended a 19-day sit-in by anti-establishment protesters at Athens University.

Officers moved in on Friday after leftist demonstrators clashed with riot police in the city centre following a miners' rally.

Thousands protested against the government's decision to block plans to develop the Skouries gold mine.

Correspondents say it was one of the most significant labour challenges since leftist Syriza came to power.

The government says all the workers' jobs are safe, and has accused the mine company of trying to blackmail Greece.

Police arrested 14 protesters after breaking up the university sit-in on Friday morning, according to local media reports.

The protesters have been occupying buildings at the site for more than two weeks, demanding the closure of maximum security prisons and the release of some suspects.

Leftist and anarchist demonstrators hurled petrol bombs and bottles at the police, who responded with tear gas and stun grenades on Thursday.

The clashes came after protests by both supporters and opponents of the Canadian-run gold mine in Skouries, in the northern Greek peninsula of Halkidiki.

The government has revoked the Eldorado Gold mining company's licence to develop the site - one of the biggest foreign investment projects in Greece - over legal and environmental concerns.

Mine workers fear they will lose their jobs at a time of high unemployment.

Prime Minister Alexis Tsipras's Syriza party won elections in January on promises to end austerity and reverse privatisations.