Toyota on Wednesday recalled 6.39 million vehicles globally over a string of problems, dealing another blow to the world's largest automaker whose reputation for quality and safety has been dented in recent years.

Despite record sales and bumper profits, Toyota has been fighting to protect its brand after earlier recalls involving millions of vehicles.

Last month, it reached a deal to pay $1.2 billion to settle US criminal charges that it covered up a sticky pedal blamed for dozens of deaths.

US rival General Motors has also been sideswiped by accusations that it hid a decade-long ignition and air bag problem linked to 13 deaths. 

There was no apparent link between GM's woes and an air bag issue that Toyota announced Wednesday as part of its broad recall.

Toyota shares were among the biggest losers in Tokyo, falling 3.07 per cent to 5,450 yen ($53) by the close.

The company issued five recalls involving 26 Toyota models, as well as the Pontiac Vibe and the Subaru Trezia, with some models affected by more than one recall. 

The Vibe, based on Toyota's Matrix model, was produced at a US factory which was jointly owned by the Japanese automaker and GM. The Trezia is a rebadged version of Toyota's Ractis subcompact. 

Toyota said "we sincerely apologise" for the recall, adding that it has "re-dedicated itself to strengthening its commitment to safety and quality". 

"In part, this means re-focusing on putting customers and people first, by listening better and taking appropriate action," the firm added.

Among the other problems are a driver's seat defect, steering column problems and an engine starter glitch that posed a fire risk.

Toyota said it had received two reports about fires due to the starter defect, but added that none of the issues had caused any accidents to its knowledge.

The affected vehicles include the Corolla sedan, the RAV4 sport utility vehicle and the Yaris subcompact.

The vehicles were made over the past decade. Toyota said the recall affects 1.08 million vehicles in Japan, 2.3 million in North America, about 770,000 in Europe and 62,000 in China, with the rest from other regions.