Shortly before the measures were approved just before midnight, some protesters hurled petrol bombs and firecrackers at police guarding the legislature. They responded with tear gas.
Greece has seen its national output shrink by a quarter since it was first forced to seek external financial aid in return for spending cutbacks in 2010.
The government, sagging in opinion polls, hopes a conclusion by lenders of its reforms progress, coupled with a restructure to bring down a mountain of overhanging debt, will allow Greece to be included in the European Central Bank’s asset-buying programme and return to bond markets in the coming months.
Athens needs aid to repay debt maturing in July.
It agreed to adopt more austerity, which will be implemented in 2019 and 2020, to convince the International Monetary Fund to participate financially in its latest 86 billion euro bailout.
To sweeten the pill, Tsipras has promised to offset the new measures with tax relief also legislated on Thursday. It will be implemented only if Greece meets its fiscal targets.
New austerity has drawn brickbats from the opposition, which has accused Tsipras of costly foot-dragging.