Germany's powerful IG Metall labour union began industrial action Sunday ahead of planned country-wide strikes in the pivotal engineering and metalworking sectors in an mounting dispute over pay. The union said more than 2,500 sector employees working in five regions had downed their tools overnight to agitate for a 6.5-percent pay hike, calling employers' offer of 3.0 percent over 14 months "a provocation". "We are calling for an offer that takes employees and their work seriously," IG Metall chairman Berthold Huber said in a statement. Among the big industrial companies hit were truck-maker MAN in Augsburg, industrial conglomerate Siemens via its Osram unit in Berlin, heavy industry giant ThyssenKrupp in Andernach and automotive parts suppliers Continental and Bosch, the union said. IG Metall said it plans "massive, country-wide" strikes from mid-week. The wage negotiations in the electrical, engineering and metalworking sectors, which employ more than 3.5 million people in Germany, are the bellwether for other key industrial sectors. Talks are currently in a third round in Germany, Europe's top economy, which has weathered the eurozone debt crisis better than most of its neighbours. Earlier this month, after several weeks of negotiations interrupted by warning strikes across the country, the two million people working in Germany's public sector secured a 6.3-percent pay hike for two years.