ATHENS, Greece -- Protesters outside Greece's parliament threw boxes of fish at police on Friday ahead of a vote that approved new austerity measures.

Members of a communist-backed labour union hurled the crates of sardines at police as lawmakers debated the cuts, which were added to draft legislation on fishing regulations in an attempt to speed up their passage through parliament.

Greece's left-wing government is trying to reach a deal on reforms with international bailout lenders that would unfreeze the flow of the country's rescue loans. Without an agreement, the country would risk default next month.

The austerity measures were approved despite strong protests from opposition parties which called the legislative manoeuvr unconstitutional.

"Apart from battering the institutions with your actions, you have added an element of farce," conservative opposition Kyriakos Mitsotakis said.

The measures, the latest in a series of major cuts, include additional restrictions on pension payments over the next five years and regulations to facilitate property foreclosures amid a growing number of distressed mortgages.

Finance ministers from countries using the euro currency will meet in Brussels on Thursday to review the Greek rescue program.

Economist Thomas Wieser, who heads a key Eurogroup advisory body, said he expected a deal next week.

"I think there's a 95 per cent probability that we'll have an agreement on June 15," he said in an Austrian newspaper interview .

The International Monetary Fund was likely to remain involved in the current rescue program but would withhold any financial contribution until a spat with European lenders over Greek debt sustainability had been resolved, Wieser said.

French Finance Minister Bruno Le Maire is due in Athens on Monday to discuss the Eurogroup meeting. He is expected to meet with Greece's Finance Minister Euclid Tsakalotos, Prime Minister Alexis Tsipras, and Bank of Greece Governor Yannis Stournaras, according to Greek officials.