The principal union in Germany's engineering and car industry called a series of short strikes Wednesday to reinforce demands for faster pay rises, dpa reported. IG Metall, which was demanding a pay hike of 5.5 per cent for 3.7 million workers, not all of them unionized, had been barred by German law from striking while it was in collective bargaining until the end of April. The employer federation had offered a rise of 2.3 per cent. Wednesday was a public holiday, but at several plants that work 24 hours a day, seven days a week, IG Metall members downed their tools when the constraint expired at midnight. At Benteler, a supplier of pressed-metal car parts in the western city of Paderborn, 400 workers refused to work part of a night shift, union spokeswoman Ingrid Gier said. About 100 workers idled two other auto industry suppliers, Essex and Nexans, for about an hour overnight. Germany's export-based economy has purred along as its neighbours flounder, prompting workers to demand a share of the bounty they have foregone during years of austerity. Chancellor Angela Merkel's government has been sending mixed signals, standing by welfare cuts but also hailing income increases for working Germans as a general election looms in September. Inflation remained tame because of the eurozone's troubles. While Wednesday's stoppages were minor, the message was clear: IG Metall is a sleeping giant that could bring German exports to a standstill. Mini-strikes were planned before the union and the employer negotiators meet again May 8.