Riot police responded with tear gas against dozens of hooded protesters who set ablaze parts of Syntagma square in central Athens as they targeted the officers, AFP journalists saw.

The violence erupted on the sidelines of a demonstration gathering 12,500 people in front of the parliament building opposed to the passage of the reforms.

Prime Minister Alexis Tsipras has angered many in his anti-austerity party and leftwing supporters by throwing his weight behind the bills, which he and eurozone counterparts agreed to on Monday in order to unlock a new rescue to debt-laden Greece worth up to 86 billion ($94 billion).