China is rapidly withdrawing its nationals from the areas worst hit by a devastating earthquake and ensuing tsunamis in Japan as severely damaged nuclear power plants there are posing a safety threat.

The Chinese Foreign Ministry issued a notice Tuesday, advising Chinese citizens to avoid traveling to Japan's quake-hit areas for the time being, while stressing that the ministry, the Chinese embassy and consulates in Japan will do everything possible to help those Chinese nationals in the disaster-hit areas leave in an orderly manner.

The Chinese embassy in Japan also posted an urgent notice on its website Tuesday, saying that the Chinese embassy and the Chinese consulate general in Niigata have taken immediate measures and will use all means possible to help Chinese nationals who are willing leave the areas worst hit by the quake.

The Chinese embassy and the Chinese consulate general in Niigata have designated some locations in Miyako, Iwate, Fukushima and Ibaraki prefectures to pick up Chinese nationals and take them to airports by bus.

The embassy said it was organizing the evacuation "due to the seriousness of and uncertainty surrounding the accident at the Fukushima nuclear plant at present."

The Japanese government said levels of radiation released by damaged reactors at the quake-stricken Fukushima No. 1 nuclear power plant were high enough to threaten human health.

Four of the complex's six reactors have been damaged by explosions. Japan's nuclear safety agency has urged residents living around the nuclear power plant to stay indoors and avoid exposure to possible radioactive substances.

There were at least 22,000 Chinese citizens in Japan after the 9-magnitude earthquake and ensuing tsunamis occurred, including some 2,900 in Iwate prefecture.

On Wednesday morning, Hu Shengcai, consul general of the Chinese consulate general in Sapporo, confirmed that most of the Chinese nationals in Iwate, one of the worst-hit prefectures, were safe.

Hu told Xinhua over the phone that the consulate general in Sapporo was trying its best to ensure the safety of Chinese nationals and help them move to safe places.

China's Red Cross Society has launched a free service on its website to help family members reunite with those who have gone missing after the catastrophic earthquake and tsunamis in Japan.

As of 3:45 p.m. (0645 GMT) Monday, some 10,746 Chinese nationals were confirmed safe in Japan, the Chinese embassy's figures showed.

China's major airlines were also quick to boost their capability to evacuate Chinese citizens stranded in Japan.

China Southern Airlines said Tuesday it had replaced the company's Airbus 321 aircraft with Airbus 300 aircraft to serve the Shenyang-Tokyo route in a bid to meet evacuation demands.

The Chinese Commerce Ministry said Tuesday that 261 Chinese nationals couldn't be reached in Japan's quake-hit regions as of 10:00 a.m. Tuesday Beijing time.

However, the ministry and the China International Contractors Association had succeeded in contacting 22,155 Chinese nationals in Japan's quake-stricken areas, and there were no reports of Chinese casualties, it said on its website.

The Chinese embassy also said Monday it had not received any casualty report of Chinese nationals following Friday's colossal earthquake in Japan.

The embassy has sent several working groups to the quake-hit areas and is still collecting information concerning Chinese nationals there.

So far, the safety of up to 8,446 Chinese has been confirmed in Japan's quake-hit areas.

The Chinese Foreign Ministry said the Chinese government attaches great importance to the safety of Chinese nationals in Japan, and has started an emergency response mechanism immediately after the earthquake.

China's tourism authorities have also reminded people to be prudent when traveling to Japan and warned Chinese tourists in Japan about aftershocks.

China's National Tourism Administration (NTA) suggested tourists avoid visiting Fukushima and Sendai, where quake damages are most severe.

As of Sunday noon, 189 Chinese tour groups with a total of 4,683 Chinese tourists in Japan had been confirmed safe with no death or injury reported, the NTA said.

The NTA has activated an emergency response system and issued a travel alert concerning Japan and countries along the Pacific Rim after the earthquake jolted Japan's eastern coast Friday.

The NTA has also called for travel agencies to protect the safety of Chinese tourists in Japan and keep in touch with the Chinese Foreign Ministry and Chinese embassy and consulates in Japan, as well as China's tourism authorities.

Chinese tour agencies had started to bring back tourists from quake-hit Japan, and many trips had been canceled.

A massive 9-magnitude earthquake struck off the east coast of Japan's main Honshu Island at 1:46 p.m. Beijing time Friday, triggering huge tsunamis along Japan's Pacific coast and causing thousands of deaths and catastrophic property damage.