Thousands of garment workers at some 30 factories in two special economic zones in Bavet City of Svay Rieng province continued striking Monday to demand a 50 U. S. dollars bonus, a trade union leader said. "Workers at those factories go on strikes Monday to demand the 50 U.S. dollars bonus pay,"said Pav Sina, president of the Collective Union of Movement of Workers, which is one of the eight opposition-aligned unions that lead the strikes. "They will protest until factories give them the bonus." Workers at the Manhattan and Tai Seng special economic zones have staged strikes since last week to demand the 50 U.S. dollars that they claimed that factories had promised to give them when they did not join a post-New Year strike, which was organized by the opposition-aligned trade unions in mid-April. However, the Garment Manufacturers Association of Cambodia ( GMAC) denied that factories had made such promise and accused the opposition-aligned trade unions of fabricating this information after they failed to attract workers for their post-New Year wage demanding strike. It said during last week's illegal strikes, workers had hurled stones at factories, threatened other workers not to work and destroyed factories' properties. "GMAC envisages that this outlawed action is evolving to violence and will spread to other industrial zones if there are no preventive measures, so we urge the Ministry of Labor and local authorities to curb these illegal strikes immediately in order to ensure security and safety for investors,"GMAC said in a statement late last week. Heng Sour, spokesman for the Ministry of Labor, could not be reached for comments on Monday. The garment and footwear industry, the kingdom's largest foreign exchange earner, comprises 960 factories with about 620, 000 workers. The sector earned 5.5 billion U.S. dollars in revenues last year. Wage dispute in the sector remains hot since pro-opposition trade unions, which represent about 19 percent of the total workers, still demand the government and GMAC to raise the monthly minimum wages to 160 U.S. dollars from the current 100 U.S. dollars.