Companies affected by the strike launched by about 3,000 members of the Finnish Union of Salaried Employees
(TU) told the Finnish News Agency
(STT) that the industrial action would have an impact within just days.
Juha Heikinheimo, the head of the cruise and ferries division of Norwegian shipbuilder Aker Yards, said the company's Finnish yards, with a total workforce of about 4,000 people, would grind to a halt in a day or a couple of days.
Outokumpu said its stainless steel production would halt very quickly while Rautaruukki, another Finnish steelmaker, assured that it could carry on with production but would have to shut down hot rolling and cutting lines.
Boliden said production at its Finnish sites would continue thanks to extraordinary measures.
Managerial and clerical workers belonging to the Finnish Union of Salaried Employees (TU) went on strike at Aker Yards, Outokumpu, Rautaruukki, engineering group Wärtsilä, miner and smelter Boliden and Luvata, formerly known as Outokumpu Copper Products.
The strike is slated to expand to apply to 4,000 employees of another 40 companies on October 31.