Violence has broken out in Athens' Syntagma Square during a mass rally demonstrating against pensions reforms.
Images from the protests show riot police dealing with outbreaks of a fire after a group of masked individuals were seen throwing rocks and Molotov cocktails at police.
Witnesses told Reuters that fights erupted between protesters and police on the sidelines of the rally, which had started out as a peaceful demonstration.
Police responded to the violence by throwing tear gas and using stun grenades against violent protesters.
Tens of thousands of Greeks took to the streets of Athens on Thursday to demonstrate against the Greek government's pension reforms, which the state is implementing to meet the demands of its international creditors as part of its third bailout.
Greek Prime Minister Alexis Tsipras is attempting to avoid pension cuts by temporarily increasing employer contributions by 1.5 per cent and reducing benefits for the richest pensioners, in a bid to cover a €600m (£459m) pension shortfall.
This is the second set of protests against the reforms in as many weeks, coinciding with a major review into the country's progress with the terms of its €86bn bailout package.
Greeks' average retirement age has been raised to 67, while pensions have been cut multiple times since 2010 by 40-45 per cent. Unions have also staged industry-wide strikes in protest against the reforms, claiming it will increase unemployment.