China will safeguard the legitimate rights and safety of its citizens and businesses in North Korea amid increasing tensions in the Korean Peninsula, Chinese foreign ministry spokesperson Hong Lei said on Sunday.

"The Chinese embassy in the Democratic People's Republic of Korea is still under normal operation," Hong said, adding that China is "seriously concerned" about the growing tension on the Peninsula.

President Xi Jinping also vowed to maintain peace and development in Asia and the world at the 2013 Boao Forum, which opened on Sunday in Hainan Province. No countries should be allowed to throw a region into chaos for selfish gains, he said.

Tensions have been running high on the Peninsula since North Korea conducted its third nuclear test on February 12 to protest against the joint military drills between Seoul and Washington.

Last weekend, Pyongyang also declared that it had entered "a state of war" against South Korea. It has also threatened to launch a preemptive nuclear strike in self-defense.

North Korean diplomats were not available to respond to telephone requests from the Global Times asking about further moves by the country.

"North Korea has grown more confident after its third nuclear test because its government believes that they are more than capable of fighting a war with South Korea and the US," Zhang Liangui, an expert on the Korean Peninsula at the Institute of International Strategic Studies at the Party School of the Communist Party of China Central Committee, told the Global Times.

Seoul said Sunday that 13 South Korean firms had been forced to suspend production at a joint industrial zone in North Korea and warned of a "critical" situation if Pyongyang continued to ban access to the site.

The US military disclosed that it would reschedule a test due in California next week as the international community grows increasingly nervous that the situation could spiral out of control, AFP reported.

Pentagon authorities revealed to AFP that the exercise might be misconstrued as suggesting that the US intended to exacerbate the current crisis.

"The Chinese government demands peace on the Peninsula, but its hands are tied with North Korea already possessing the power to start a war. What China needs to do now as well as call for peace keeping is to evacuate its Chinese firms," Zhang said.

However, tour services to North Korea from Dandong, Liaoning Province, are still operating normally.

"There are customers asking about whether the group tours have been suspended. But currently the tours are still very popular and the situation is stable," an anonymous employee from the Jinhangxian tourist agency in the city, told the Global Times.

Hu Qingyun and agencies contributed to this story