China on Monday called for restraint after South Korea and US troops launched a joint military drill and Pyongyang reportedly severed a communications hotline with Seoul.

"Now the situation on the peninsula is highly complicated and sensitive. China maintains that it shall be in the fundamental interests of the international community to safeguard the peace and stability of the peninsula and Northeast Asia," Chinese foreign ministry spokeswoman Hua Chunying said at a regular press briefing.

China urged all parties to remain calm and refrain from any actions that may escalate tensions, Hua said.

South Korean and US troops started their annual military exercise Monday despite North Korea's earlier threat that it would scrap the Korean War Armistice Agreement and sever an inter-Korean communications hotline if the two parties did not stop the drill.

North Korea's official Rodong Sinmun newspaper confirmed Monday that the armistice had been nullified as it had promised earlier. "With the ceasefire agreement blown apart, no one can predict what will happen in this land from now on," the newspaper said, according to AFP.

Pyongyang last week threatened to strike the US mainland with a long-range nuclear missile and turn Washington into a "sea of fire," although analysts believe North Korea has not yet acquired the ability to launch smaller nuclear warheads, which is necessary for intercontinental missile programs.

South Korea's unification ministry also said Monday that the North had severed the inter-Korean hotline, which is used for communication between the two Koreas, which do not have diplomatic relations.

AFP quoted a spokeswoman for South Korea's unification ministry as saying that the two sides habitually speak twice a day, but "the North did not answer our call this morning."

"North Korea's decision to sever the hotline and scrap the armistice has undoubtedly pushed tensions to extremes. Pyongyang wanted to use brinkmanship to force the international community, especially the US, to reengage with it," Cui Zhiying, director of the Korean Peninsula Research Center at the Shanghai-based Tongji University, told the Global Times.

Lü Chao, director of the Korean Research Center at the Liaoning Academy of Social Sciences, said although North Korea's war rhetoric is ostensibly targeted at the South Korea-US drill, it is actually aimed at showing defiance to the recent international sanctions against its nuclear test.

"The drill is only an annual activity and such harsh rhetoric from Pyongyang is rare," he told the Global Times.

The two-week Key Resolve computer-simulated drill involves 10,000 South Korean and about 3,000 US troops.

"This year is particularly important, because it is the first time the South Korea Joint Chiefs of Staff have planned and executed this combined exercise," said US General James Thurman, Combined Forces Command commander, according to South Korea's Yonhap news agency.

South Korea is scheduled to assume wartime operational control of the combined forces from the US in December 2015.

"The escalation of the Korean Peninsula tension might give the US an excuse to delay the handover of wartime operational control to South Korea," said Cui.

Meanwhile, South Korea's defense ministry said Monday that North Korea is also expected to carry out large-scale unprecedented military drills in its eastern province.

"The North Korean military is believed to have intensified military training in light of Key Resolve. Currently, no special activities are being observed in the North," the Yonhap News quoted Kim Min-seok, a spokesman for South Korea's Defense Ministry as saying.

Without the armistice, the North and the South are actually in a state of war, so it would not be a surprise if a smaller conflict broke out between the two sides in border areas, which have been flash point throughout the history of the peninsula, Lü warned.

North Korea fired artillery shells at South Korea's Yeonpyeong Island in November 2010, killing four South Koreans in what Pyongyang described as a response to a military drill between South Korea and the US near the maritime border.

Agencies contributed to this story