Police have clashed with protesters throwing rocks and Molotov cocktails at an anti-austerity rally outside parliament in Athens.

The violence came as Greek MPs got ready to hold a crucial vote on measures they must approve by the end of the day in order to secure a $127 billion bailout deal.

Prime Minister Alexis Tsipras has said he doesn't believe in the agreement's austerity measures but that it was the best possible deal he could get to prevent Greece from being forced out of the eurozone.

Sky's Alex Rossi is in Athens with the protestors, who are unhappy with the austerity measures.

"The aim of this is to disrupt the agreement."

A number of government MPs say they'll resign, rather than vote yes - but there are enough government and opposition MPs who will vote to see it pass.