Countries in the world have called for stability and restraint on the Korean Peninsula after the Democratic People's Republic of Korea (DPRK) Monday announced the death of its top leader Kim Jong Il.

Kim, who was general secretary of the Workers' Party of Korea, chairman of the DPRK National Defense Commission, and supreme commander of the Korean People's Army, died "from a great mental and physical strain at 08:30 (2330 GMT Friday) on Dec. 17, 2011, on a train during a field guidance tour," the DPRK's official KCNA news agency said.

China on Monday offered its "deep condolences" on the death of Kim.

"We are shocked to learn that DPRK top leader comrade Kim Jong Il passed away and we hereby express our deep condolences on his demise and send sincere regards to the DPRK people," said Foreign Ministry spokesman Ma Zhaoxu.

The White House said late Sunday that the United States is in close touch with South Korea and Japan over Kim's death and remains committed to stability on the Korean Peninsula.

"We are closely monitoring reports that Kim Jong Il is dead," White House spokesman Jay Carney said in a statement.

"We remain committed to stability on the Korean Peninsula, and to the freedom and security of our allies," he added.

U.S. President Barack Obama held a phone conversation with South Korean President Lee Myung-bak following Kim's death, the White House said Monday.

Obama reaffirmed U.S. strong commitment to the stability of the Korean Peninsula and the security of South Korea, it said a statement.

Meanwhile, South Korea is on high alert following the death of Kim.

Immediately after the KCNA reported Kim's death, President Lee convened the National Security Council to discuss follow-up measures with officials including the foreign minister and the defense chief.

Lee also ordered all government employees be on emergency alert, a measure that would restrict their unauthorized leaves.

Japan has already discussed Kim's death with the United States and South Korea. Prime Minister Yoshihiko Noda urged officials to keep in touch with the United States, China and South Korea over the issue, Kyodo cited a senior government official as saying.

Noda also urged officials to make full preparations for contingencies while Foreign Minister Koichiro Gemba asked the foreign ministry to prepare for any events after Kim's death.

Chief Cabinet Secretary Osamu Fujimura told reporters that Japan hopes Kim's death has no negative impact on Korean Peninsula security.

Meanwhile, Australian Foreign Minister Kevin Rudd said Monday that world countries and leaders should maintain calm and restraint over Kim's death.

Rudd said he has spoken with the South Korean ambassador not long before and the Australian government will keep close contacts with allies in the region.

New Zealand Prime Minister John Key said Monday that he does hope for a smooth transition in the DPRK and a better outlook for the DPRK people.