The Pro—trade union said some 1,000 office workers at paper mills of UPM—Kymmene Corp. started the walkouts after several rounds of negotiations failed.

Hundreds of Finnish workers on Wednesday started a two-week strike at plants owned by the world’s largest magazine paper marker in an effort at speeding up stalled wage talks.

The Pro—trade union said some 1,000 office workers at paper mills of UPM—Kymmene Corp. started the walkouts after several rounds of negotiations failed.

“We chose only UPM this time so that we could put some pressure on the employers,” Pro chairman Antti Rinne said.

He did not give details of the talks between the union and employers’ organizations, which broke down on Monday under the mediation of the national arbitrator. No further talks have been announced.

UPM said the strikes likely would cause some mill closures within days and could cause “millions of euros (dollars)” of damage.

“The continuous disturbances on the labour market damage Finland’s reputation and the repeated strikes will shift orders permanently to other locations from the Finnish production units,” said Jyrki Ovaska, president of UPM’s paper business group.

UPM, like other European forest product companies, has been hit by overcapacity forcing it to close mills, cut production and lay off thousands of workers. Also, strikes by Finnish paper workers have cost companies millions in lost earnings.

The Finnish Forest Industries Federation also warned that the union was “jeopardizing its members’ jobs” in Finland.

Finland is the world’s sixth—largest producer of pulp, paper and paperboard, providing work for some 200,000 people. UPM, which employs 22,000 workers worldwide, has production plants in 15 countries.

More than 3,000 people are covered by the collective labour agreement for salaried paper industry employees. Disagreement hinges on pay hikes, working conditions and the terms of a new labour contract.