Nippon Steel said it had filed patent infringement lawsuits against Toyota and China’s Baoshan Iron & Steel with a Tokyo district court.

Nippon Steel is seeking JPY20bn (US$176m) in damages from each company, alleging the two firms have infringed on its patents on non oriented magnetic steel sheets that are used in electric vehicles, it said in a statement cited by Reuters.

Toyota said in a statement to Reuters the suit was “very regrettable” and that it had found no patent infringement issues before it signed a supply deal with the steelmaker.

A Baosteel spokesperson had no immediate comment to the news agency.

In a rare lawsuit against its key customer, Nippon Steel has also filed a petition for a preliminary injunction prohibiting Toyota from manufacturing and selling motor driven vehicles which use the electrical steel sheets allegedly violating its patents.

“The electrical steel sheets are indispensable materials for automobile electrification and are one of our key products aimed at helping decarbonisation for cars, electrical products and power plants” a Nippon Steel spokesperson said.

The company had decided to take legal action as it could not reach a resolution through discussions with both companies, it said.

This was the first time Nippon Steel had filed a patent infringement lawsuit against Toyota, the spokesperson added.

The steelmaker declined to give further details to Reuters, including the names of the Toyota products and the size of their sales.