ATHENS (Reuters) - Greek lawmakers looked set to endorse a new austerity deal on Sunday to secure an EU/IMF bailout and avoid national bankruptcy, defying public rage and protesters who fought pitched battles with riot police outside parliament.

Lawmakers came under immense pressure from both sides, with tens of thousands of demonstrators pouring into Syntagma Square before parliament, while the government warned that rejection would demand "unimaginably harsher" sacrifices by Greeks.

Black-masked protesters threw petrol bombs, creating a wall of fire, and homemade bombs made from gas canisters as riot police advanced across the square on the crowds, firing tear gas and stun grenades. Loud booms could be heard inside parliament.

"Tear gas has reached the parliament chamber," said leftist lawmaker Panagiotis Lafazanis.