Kobe Steel, Japan's third-biggest steelmaker, admitted earlier this month that it had falsified specifications on the strength and durability of its products. The falsifications stretch back for more than 10 years, a senior executive told Reuters.

"This is a problem between companies, but we want to be actively involved in the issues," Seko told a news conference, adding that he hoped Kobe Steel would take proper and prompt actions to remedy the situation.

Japan's Transport Minister Keiichi Ishii also urged the company to investigate the falsifications and take proper prevention measures.

"It was extremely regrettable," Ishii told a news conference on Friday.

"We want the company to take measures to make sure that it complies with laws and reinforces safety management," he said.

The ministry has also asked Kobe Steel's customers to ensure the safety of automobiles and planes.

No safety problems have surfaced as Kobe Steel attempts to confirm the extent of the data tampering. But in Europe, aviation safety authorities earlier this week issued a directive advising aircraft manufacturers to avoid using Kobe Steel products if they can until checks are completed.

Four Japanese automakers on Thursday said they found no safety issues with aluminum parts supplied by Kobe Steel, allaying some concerns that falsified quality data on products from the steelmaker had compromised their vehicles.

Nonetheless, the company's fate hangs in the balance while checks are being carried out. It must report to Japan's industry ministry by around the end of next week on any safety concerns and provide a more extensive account of the problems a fortnight later.

(Reporting by Ami Miyazaki, Yoshiyasu Shida and Yuka Obayashi; Editing by Kenneth Maxwell)