Image copyright AFP Image caption The strike shut the Athens metro system

Greeks have begun a three-day general strike in protest at further austerity measures that are being proposed in return for more bailout money.

Shipping, public transport and civil service departments were among sectors hit in a bid to stop the introduction of tax and pension changes.

The sudden 48-hour strike on Friday and Saturday was called in addition to action previously planned for Sunday.

Greece's left-led government is due to a vote on the tax changes on Sunday.

The next tranche of about €5bn (£4bn) is overdue, after talks with Greece's international lenders faltered over the pace of reforms.

Unions said a proposed overhaul of the pensions system and rises in social security contributions were designed to win favour with eurozone finance ministers, who are due to discuss Greece's bailout money on Monday.

Greece's largest labour union, the private sector GSEE, said the changes, were the "last nail on the coffin" for workers and pensioners. A spokesman said: "They are trying to prove to the Eurogroup that they are good students but they are destroying Greece's social security system."

In Athens, no public transport service was working on Friday morning as metro, tram, bus and rail workers refused to work.

Train services across the country were halted, and ferries linking mainland Greece to the islands remained anchored in port. The strike by the powerful PNO seafarers union's strike is set to last until Tuesday morning.

Air travel was not affected by the strike. Airport workers staged their own industrial action last month.

The nationwide strikes are the fourth to be called since Prime Minister Alexis Tsipras's government won re-election after organising a referendum on the country's bailout.

Mr Tsipras was elected on an initial anti-austerity pledge but later signed up to Greece's third international bailout since 2010. He has a thin majority with 153 MPs in a 300-seat parliament.