Hanoi - More than 1,500 workers at a South Korean-owned garment factory in the Vietnamese port city of Haiphong have been on strike for three days, a factory official said Wednesday.

Do Thi Van, head of human resources at the Viet-Han garment company, said the workers were demanding base salary increases and changes to the way bonuses are awarded.

"Some of their demands are unreasonable, so the company cannot satisfy them," she said.

Van said the company could not raise workers' base salary, set at 63 dollars per month, as it was already above the national minimum wage of 60 dollars.

But the company said it would consider reducing the number of products a work group is required to finish each hour in order to receive bonus pay from the current 30, a rate workers say is impossible to meet.

Workers said they would resume work on Thursday pending resolution of the dispute.

Representatives of Vietnam's national trade union in Haiphong were not available for comment.

In Vietnam, strikes are typically launched independently by informal groups of workers. Local government and union officials then negotiate between workers and management. They are not exclusively loyal to workers' interests, but take government and company interests into account.

The latest available figures from Vietnam's national trade union showed there were 46 wildcat strikes in the first three months of 2009, compared with 113 cases in the same period last year.

Strikes rose in 2008 due to high inflation. In 2009, they have slowed, in part due to worker anxiety over job security. (dpa)