Nuclear situation 'grave' Japan PM warns: Fukushima nuclear plant unpredictable as officials fear breach at one reactor

Japan's prime minister has warned the situation at the country's quake-hit nuclear power plant remains "unpredictable" after officials said they suspected a breach in the reactor core of a unit at the complex.

"The current situation is still very unpredictable. We're working to stop the situation from worsening. We need to continue to be extremely vigilant," Naoto Kan said on Friday.

He also praised emergency workers at the Fukushima Daiichi plant in northeastern Japan, which was hit by a massive earthquake and tsunami two weeks ago, for "risking their lives" in the battle to control the situation.

Earlier, officials from the plant's operator said there was possible damage at reactor number three at the complex, meaning more radioactive contamination may have leaked into the environment.

"It is possible that the pressure vessel containing the fuel rods in the reactor is damaged," a spokesman from Tokyo Electric Power Co (TEPCO) told the AFP news agency.

Japan's nuclear safety agency said radioactive substances had leaked to places "far from the reactor".

"As far as the data show, we believe there is a certain level of containment ability but it's highly possible that the reactor is damaged," Hideyuki Nishiyama, a spokesman for the agency, said.

Reactor number three is of particular concern because it uses a potentially volatile mix of uranium and plutonium.

Several workers at the plant were evacuated on Thursday with suspected radiation burns and a further two workers were taken on Friday morning after radiation-contaminated water seeped over the top of their protective boots, the AP news agency said. (read more)