German industrial conglomerate Siemens is expected Thursday to announce a massive restructuring plan in its limping energy business that could see thousands of employees lose their jobs.

Unions have vowed to resist any layoffs, as they would follow on the heels of flourishing annual results for the sprawling group.

"We have to tackle structural issues in some individual businesses" in the coming financial year, chief executive Joe Kaeser said last week -- even as Siemens reported 11-percent growth in net profit for 2016-17, to 6.2 billion euros ($7.3 billion).

The Munich-based group -- whose products range from trains to wind turbines to medical equipment -- has already announced some 6,000 job cuts in its wind power unit.

Falling prices in major markets like India and the US bore most of the blame for the layoffs, Siemens said of the division, which merged with Spain's Gamesa earlier this year.

Meanwhile, German weekly Manager Magazin reported that Siemens' fossil fuels division, one of Siemens' largest with some 30,000 employees, could shutter 11 of its 23 sites worldwide.

Markets for the unit's products such as natural gas turbines were shrinking as a result of "global energy trends" away from fossil fuels, the group said.

Powerful union IG Metall fears managers could slash a four-digit number of jobs, most of them in Germany.

Kaeser, who has already presided over massive changes at Siemens since taking the reins in 2013, said only that "painful cuts" would be announced at a Thursday works council meeting.

He added that he would try to "soften the blow" by reassigning or retraining workers.

"We will have to start a discussion of creative forms of resistance" if bosses press on with site closures and layoffs, IG Metall board member Juergen Kerner warned in a Wednesday interview with WirtschaftsWoche magazine.