It's the latest installment in a week of furious rhetoric from the North, fueled by its anger over the U.N. vote on the new sanctions, a response to the Pyongyang's recent nuclear test, and joint military drills by the United States and South Korea, which take place in the region each year.

North Korea watchers and U.S. officials say that the recent frenzy of ominous language from North Korea under its young leader Kim Jong Un makes the situation on the Korean Peninsula more worrying and unpredictable. South Korea has warned the North that it will retaliate strongly and sternly if its citizens are threatened.

"This surge in provocative rhetoric is particularly dangerous," said Michael Auslin of the American Enterprise Institute. "South Korea's new president (Park Geun Hye) can't be seen to back down in the face of the North's threats, while Kim Jong Un may feel that his successful missile and nuclear tests give him the ability to keep pressuring Seoul. The two may wind up talking themselves into conflict."

South Korean President Park Geun-hye, who took office late last month, said Friday that Seoul would respond strongly to any provocation from Pyongyang, the semiofficial news agency Yonhap reported. The possibility of flare up was highlighted by the Washington-based Center for Strategic and International Studies, which predicted a provocative move from the North "in the coming weeks." The center said that according to its research, Pyongyang has carried out "a military provocation of some form within weeks of every South Korean presidential inauguration dating back to 1992." A military clash could risk drawing in the United States, which has about 28,500 troops stationed in South Korea as part of the security alliance between the two countries.

The most recent skirmish between the two Koreas took place in November 2010, when the North shelled an island on the South's side of the border, killing several people. Pyongyang claimed Seoul had provoked it by carrying out training exercises off their shared coast.

A week of strong threats

The North's comments Friday doubled down on statements it had made earlier this week, promising to abolish the armistice agreement that stopped the Korean War in 1953, and threatening strikes on the United States and South Korea.

Claiming its enemies are "hell bent on confrontation and war fever," Pyongyang said it was now revoking "all agreements on nonaggression reached between the north and the south," a declaration it has made in previous years. It also said it was nullifying the joint declaration on the denuclearization of the Korean Peninsula. The North, which conducted its third underground nuclear test last month, had said recently that denuclearization of the region was "impossible" because of what it described as the United States' hostile policy toward it.

And it stated that it was immediately cutting off the "north-south hotline," three days after it had already said it planned to terminate its military telephone line with the United States. The phone line is meant to serve as a tool to defuse potential flash points along the heavily militarized border between the two Koreas.

But Andre Kok, deputy public affairs officer for U.S. Forces in Korea, said that reports of the North's Korean People's Army (KPA) cutting off communication often arise when military training exercises are taking place, as they are at the moment. "When we place a call on the direct phone line and the KPA does not answer, we have no way of knowing if the KPA has actually disconnected the phone lines or are just not answering the phone," he said.