SEOUL, South Korea -- North Korea has canceled the 1953 armistice that ended the Korean War, a state-run newspaper in the North said Monday, following days of increased tensions over its latest nuclear test.

A UN spokesman said North Korea cannot unilaterally dissolve the armistice.

North Korea also followed through on another vow: It shut down a Red Cross hotline the North and South used for general communication and to discuss aid shipments and separated families' reunions.

Enraged over the South's joint military drills with the United States and last week's added UN sanctions imposed on Pyongyang for its Feb. 12 nuclear test, North Korea has piled threat on top of threat, topped off with a vow to launch a nuclear strike on the United States.

Seoul has responded with tough talk of its own and has placed its troops on high alert. Tensions have reached their highest level since North Korea rained artillery shells on a South Korean island in 2010.

The North Korean government made no formal announcement on its repeated threats to scrap the 60-year-old armistice, but the newspaper Rodong Sinmun reported that the armistice was nullified yesterday by Pyongyang as it had said it would.

The North has threatened to do so several times before, and in 1996 it sent hundreds of troops into a border village. They withdrew later.

UN spokesman Martin Nesirky said the armistice is still in force because the agreement was adopted by the UN General Assembly and neither the North nor South could dissolve it unilaterally.

The Obama administration expressed heightened concern over North Korea's threats of war as it issued new sanctions against the communist nation's primary exchange bank and against several senior government officials.

Latest videos

Newsday LogoYour Island. Your Community. Your News.Digital AccessOnly 25¢for 5 months