Greek police have fired pepper spray at retirees taking part in an anti-austerity protest against pension cuts in central Athens near the prime minister's office.

About 1,000 people, some of them with canes, took party in Monday's protest. Dozens of protesters at the front of the rally tried to break through a police cordon and chanted "Shame on you, shame on you!"

The protesters were trying to tip over a riot police bus when officers fired the pepper spray.

Greece's left-wing government has imposed new cuts on pensions this year as part of its bailout commitments to international lenders, with the International Monetary Fund pressing for deeper cuts.