Train drivers at Germany's national railway have started a two-day strike after their union rejected a new pay offer in a bitter dispute complicated by rivalry between unions.

The GDL union called members out on strike from early Saturday morning until early Monday morning, its second walkout this week.

GDL wants a 5 percent pay increase and shorter working hours. A bigger sticking point is its demand to negotiate for other staff traditionally represented by a rival union.

National railway Deutsche Bahn says it offered a raise of 5 percent over 30 months on Friday for the drivers but won't accept rival pay deals for other employees. GDL rejected what it called a "sham offer."

Deutsche Bahn aimed to operate 30 percent of scheduled long-distance trains.