Workers across Greece launched a general strike Thursday to protest an unpopular pension overhaul that has sparked a major backlash against embattled leftist Prime Minister Alexis Tsipras. 

The 24-hour industrial action -- the third general strike in as many months -- has stopped train and ferry services and grounded dozens of flights.

Hospitals will operate on emergency footing, petrol stations will remain closed and taxis have been pulled off the streets.

Lawyers, truck drivers and farmers are also participating in the walkout.

The farmers have formed protest hubs at dozens of locations on Greece's national highways, intermittently blocking traffic with tractors over the past two weeks.

On Tuesday, the farmers blocked freight trucks from travelling into Bulgaria and Turkey, causing long lines on the respective borders.

The strikers are furious at government plans to lower the maximum pension to 2,300 euros ($2,500) per month from 2,700 euros currently and introduce a new minimum guaranteed basic pension of 384 euros.

Tsipras's leftist administration also wants to merge pension funds and increase social security contributions by both employers and staff.

The plan has come under fire from a wide array of professional classes, from lawyers and engineers to sailors and farm workers.

Critics say the new system penalises those who dutifully pay their pension contributions over a lifetime of work and will encourage undeclared labour practises.

But Greece must save 1.8 billion euros from state spending on pensions under a three-year bailout signed with the European Commission, the European Central Bank and the International Monetary Fund in July.

The Tsipras government has warned the nation's pension system will soon collapse without the reform, which is expected to be put before parliament for a vote later this month, where the prime minister has only a razor-thin majority.

However, the government has rejected claims that the disputed overhaul has cast doubt over its survival.

The Tspiras government has only a majority of 153 deputies in the 300-seat parliament.

"The government majority (in parliament) is strong and cohesive," government spokeswoman Olga Gerovassili said Tuesday.