Clashes have broken out between Greek police and youths throwing fire bombs and stones, after 40,000 protesters joined anti-government demonstrations through central Athens in protest against planned pension-policy changes.
Police used tear gas and stun grenades on Thursday against dozens of hooded anarchists outside the parliament and other parts of the city centre.
Protests were also held in at least a dozen other Greek cities and towns, where several rallies were joined by protesting farmers driving their tractors.
Unions are angry at pension-policy changes that are part of Greece's third international bailout.
The government, which is led by the left-wing Syriza, is trying to overhaul the pension system by increasing social-security contributions to avoid pension cuts.
But critics say the changes will lead many to pay up to three-quarters of their income in pension contributions and taxes.
Opposition to the reform has been widespread.
It has united a disparate group of professions, including farmers, artists, taxi drivers, lawyers, doctors, veterans and engineers.
Al Jazeera's John Psaropoulos, reporting from Athens, said: "This is the third general strike since Syriza capitulated to austerity. Like the others, it has been initiated by the Communist Party which has a vested political interest in showing up the government.
"But unlike the other two, it has the support of the urban middle class and the countryside."
Series of conditions
The strike comes as international bailout inspectors meet George Katrougalos, Greece labour minister, to discuss the pension reforms.
The government has to meet a series of conditions to get money from its third international bailout, which is worth about $89bn.
Having cleared the first set of conditions, it is now discussing the next batch of reforms required.
Once cleared, it will be due further funds from the bailout as well as a promise to discuss the size of Greece's debt burden, which, despite years of austerity, still stands at a staggering 175 percent of the country's annual GDP.
The pension changes are difficult for Syriza, which, while still in opposition, had led protests against it.
However, Alexis Tsipras, Greece's prime minister, was forced to abandon his earlier stance when faced with the stark choice of signing up to a third rescue package or the country having to leave the euro currency.
