A two-day general strike was launched on Tuesday by Greece's main labor unions, GSEE and ADEDY, as the country's Parliament prepares to vote on a new round of austerity measures demanded by foreign lenders.

On Tuesday, a few thousands joined a march in Athens in protest against the 13.5 billion euros of proposed cuts and tax increases over the next two years, which include a rise in the retirement age to 67 as well as pensions being cut by up to 15 percent for workers who make more than 1,000 euros per month.

However, the head of the private sector union GSEE, Yannis Panagopoulos, on Tuesday appeared unhappy about the size of the protest.

“Unfortunately, the turnout in today's rally is not as big as it should be,” he said in a radio interview, putting the blame on a decision by public transport workers to strike on the same day.

Parliament is set to vote on the austerity package on Wednesday. The outcome of the vote is far from certain, due to disagreements in the conservative-led coalition government and a reluctance among center-left lawmakers to swallow yet another bitter austerity pill.