Toyota Chairman Akio Toyoda apologised Monday for massive cheating on certification tests for seven vehicle models as the automaker suspended production of three of them.

The wide-ranging faulty testing at Japan's top automaker involved the use of inadequate or outdated data in collision tests, and incorrect testing of airbag inflation and rear-seat damage in crashes. Emissions tests also were found to have been falsified.

Toyota Motor Corp, based in Toyota city, central Japan, suspended production in Japan of the Corolla Fielder, Corolla Axio and Yaris Cross. The faulty tests were also found on models already discontinued.

The company said the wrongdoing does not affect the safety of the vehicles already on roads, which include the Corolla subcompact and Lexus luxury vehicles.

“We sincerely apologise,” Toyoda said, bowing deeply at a news conference in Tokyo.

A Japanese government investigation into Toyota began in January. The latest problems don't pertain to Toyota's overseas production.

Also Monday, Japanese rival Mazda Motor Corp reported similar irregular certification testing, and halted production of two models, the Roadster and Mazda 2. It said incorrect engine control software was used in the tests.

Mazda, based in the southwestern city of Hiroshima, also acknowledged violations on crash tests on three discontinued models. The violations don't affect the vehicles' safety.

About two years ago, certification problems surfaced at Toyota group companies, truck maker Hino Motors and Daihatsu Motor Co, specialising in small models, and Toyota Industries Corp., which makes machinery and auto parts.

Shinji Miyamoto, a Toyota executive overseeing customer satisfaction, said Toyota began looking into its own tests following the problems at the group companies.

The apparent unravelling of the testing systems at Toyota and its group companies is an embarrassment for an automaker that's prided itself for decades on production finesse and a corporate culture based on empowering workers to make “ever-better cars”.

Toyoda said the company may have been too eager to get the tests done and abbreviated them at a time when model varieties were burgeoning.

Toyota sells more than 10 million vehicles around the world.

Toyoda, the grandson of the company's founder, suggested some certification rules might be overly stringent, noting such tests differed around the world. But he repeatedly said he wasn't condoning the violations.

“We are not a perfect company. But if we see anything wrong, we will take a step back and keep trying to correct it,” said Toyoda.