Greek riot police have carried out a pre-dawn raid on a train depot in Athens on Friday where striking workers had barricaded themselves.
The Government issued an emergency decree, ordering staff on the city's metro system to end their protest, which started eight days ago.
Workers had been on the ninth successive day of strike action that had crippled the underground system, the BBC reports.
The government used an emergency law to threaten the strikers with arrest unless they went back to work. It was not clear if the move would lead to transport resuming.
Strikers are opposed to proposals which might see their salaries slashed.
The operation took place before dawn, with around 100 riot police officers entering the depot where workers had barricaded themselves in overnight.
A police spokesman told the BBC that three people were arrested and subsequently released. The area around the depot has now been cordoned off to prevent others from joining the strike.
Bus drivers and railway workers were to join the strike later on Friday morning.
Transport unions say they will continue their action, raising the possibility that some could face arrest and criminal charges, with a prison sentence of up to five years.
The Government is using civil mobilisation legislation, which has only been invoked nine times since the collapse of Greece's military dictatorship in 1974.
Workers on the underground had been striking over a public sector unified wage scheme that would see their salaries reduced by up to 25%.
This is now becoming a significant stand-off and a test of the government's resolve over austerity measures opposed by trade unions, the BBC reports.
Public opinion is split over the issue, but with commuters facing long taxi queues as temperatures fall, the Government feels that it may just get the support it needs to hold firm.
Greece has been kept solvent by huge rescue loans from its European Union partners and the International Monetary Fund since May 2010.
Under the terms of the rescue funds, Greece has agreed to substantial spending cuts, such as redundancies and pay freezes in the public sector, and reduced pensions. The unemployment rate hit 26.8% earlier in January.