A quarter of Serbia's police force - around 13,000 employees - went on a work-to-rule Thursday as the country continues to struggle with a deep economic downturn that has seen inflation eat away at workers' wages, according to dpa. The police will only do the legal minimum required of their jobs, union leader Velimir Barbulov said. "We will not do field work, except in cases of major disturbances and for rescue efforts," he said. The strikers are demanding a 40-per-cent wage hike and say they will not end their protest until their demands are met. The independent police union decided to launch the work-to-rule stoppage despite opposition from other police organizations. The police action is the second potentially crippling strike to hit Serbia in recent days. Elementary and high-school teachers launched a work stoppage last week, but their strike has hardly gotten off the ground. Serbia has been hit hard by recession and has imposed austerity measures, including a freeze of civil servant wages, in return for a loan from the International Monetary Fund. The local currency, the dinar, has lost around half of its value over the past three years, with inflation steadily in double digits. The average monthly wage now equals about 400 dollars.