Akhir 20, 1432 H/March 25, 2011, SPA -- Several thousand striking teachers and their supporters rallied Friday in the Serbian capital, Belgrade, demanding higher wages, according to dpa. The demonstration, which took place in a square in central Belgrade, was organized by one of the country's four teachers' unions. The teachers, who went on strike in January, have been seeking salary increases of 20 per cent. Three of the unions went back to work in February after the government promised a 15-per-cent wage hike. The union said that, instead of imposing wage cuts, the authorities should crack down on corruption. Speaking separately, Prime Minister Mirko Cvetkovic said he did not understand the protest and promised that striking teachers will get paid after they hold classes their students missed. "I am mystified, because the government met all its promises," Cvetkovic told reporters. He downplayed the impact of the stoppage, stressing that the most schools were working normally. Hit hard by the world economic crisis, Serbia has promised to implement cost-saving measures in exchange for a International Monetary Fund standby credit.