Toyota on Monday resumed operations at all its domestic plants that had been halted since the March 11 earthquake and tsunami, with production volume still at around 50 per cent due to a parts shortage.

The auto giant said it had begun measuring the radiation levels of its export vehicles, parts for overseas assembly and service parts and found no abnormalities amid Japan's ongoing nuclear crisis.

Of the Toyota group's 18 assembly plants in Japan, three had already been in operation and the rest resumed production on Monday, according to the Japanese auto giant.

"The plants are operating with about 50 per cent of production due to the shortage of auto parts," a Toyota spokeswoman said.

The firm plans to continue at the current capacity until 3 June, with production halting during the Golden Week holiday between late April and early May.

The plants that resumed operation on Monday included sites in quake-hit Miyagi and Iwate prefectures.

A component supply crisis has strangled auto production in Japan and enforced a slowdown overseas in the wake of the 11 March disasters, and analysts say it will last several months amid continued power outages.

Japan's biggest ever quake and the tsunami it unleashed shattered supply chains and crippled electricity-generating facilities, including the stricken Fukushima Daiichi nuclear power plant, which is at the centre of an ongoing atomic emergency.

Many key component manufacturers are based in the worst-hit regions of Japan, their facilities damaged by the 9.0-magnitude earthquake or inundated by the giant wave that followed.

The impact has been acute for automakers the world over, with companies shutting plants or slowing production as far afield as Britain, the United States, Turkey, France, Australia, Poland and the Philippines.