The maximum level of exposure for workers is 250 millisieverts for the duration of their work at the plant [Reuters]

A worker at Japan's tsunami-crippled Fukushima Daiichi nuclear power plant has died, plant operator Tokyo Electric Power Co said, bringing the death toll at the complex to three since a massive earthquake and tsunami in March.

The cause of the death was unknown. The man, in his 60s, was employed by one of Tokyo Electric's contractors and started working at the plant on Friday.

He was exposed to 0.17 millisieverts of radiation on Saturday, Tokyo Electric said.

The Japanese government's maximum level of exposure for male workers at the plant is 250 millisieverts for the duration of the effort to bring it under control.

The worker fell ill 50 minutes after starting work on Friday evening and was brought to the plant's medical room unconscious. He was later moved to a nearby hospital and confirmed dead, a Tokyo Electric spokesman said.

Working conditions at the plant are harsh. Goshi Hosono, a special adviser to Prime Minister Naoto Kan and a ruling Democratic Party lawmaker, voiced concerns about the working environment at the Fukushima complex on Wednesday.

"I would like to spend my energy to improve working conditions. Many people told us working environment (at the plant) is way too bad," Hosono told a news conference.

The magnitude 9.0 earthquake and tsunami on March 11 triggered cooling system malfunctions at the plant, and caused radiation to leak into the atmosphere and the ocean.

Engineers are still struggling to bring the plant under control. Two Tokyo Electric employees went missing while patrolling the plant soon after the quake and were later found dead.

Source: Agencies