North Korea test-fired a short-range missile off its west coast last week in the first such launch for 19 months, South Korean sources said Wednesday.

The launch was seen as a routine test to improve the country's missile capability, the sources said, declining to give details. The defense ministry had no comment.

North Korea said Monday it would no longer deal with South Korea and threatened to retaliate against any moves by Seoul to wage "psychological warfare".

The North's powerful National Defense Commission (NDC) said in a statement it would also cut a military communications line on the east coast and shut a liaison office at the jointly-run Mount Kumgang resort.

An American citizen detained in North Korea since November on unspecified charges was Saturday on a plane heading back to the United States with a U.S. delegation, Chinese state media reported.

Official Chinese news agency Xinhua said that a team from the U.S. State Department had flown out of communist North Korea with the detained man.

North Korea said Friday it has decided to release a U.S. citizen held since November on unspecified charges, following requests from a U.S. official who is assessing possible food aid.

Eddie Jun Yong-Su, a California-based businessman, was detained for apparent missionary activities in the hard line communist state, colleagues say.

The United States on Tuesday announced it is imposing sanctions against seven foreign firms, including Venezuelan, Singaporean, and Israeli companies, as part of efforts to check Iran's nuclear ambitions.

It also imposed sanctions against 16 other foreign firms and individuals, including from China, over trade with Iran, Syria and North Korea in goods or technology that may be used for weapons of mass destruction or missiles.

South Korea is spending millions of dollars to fortify shelters on five frontline islands near its tense sea border with North Korea in case of any future attacks, an official said Monday.

The move follows an artillery and rocket barrage by the North last November against Yeongpyeong Island, which killed two marines and two civilians. The South has sent more troops and weaponry to the islands since the attack.

South Korea launched a major live-fire drill Thursday near the tense land border with North Korea in a show of strength marking the first anniversary of the sinking of one of its warships.

Tanks, armored personnel carriers, artillery pieces, helicopters and jets took part in the drill at the Pocheon range, 30 kilometers south of the border, the defense ministry said.

North Korea Tuesday threatened a military response to ongoing U.S.-South Korean military drills, blasting them as preparations for a nuclear war of aggression against it.

Seoul and Washington say the annual war games which began Monday are routine and defensive in nature, but Pyongyang calls them a rehearsal for invasion.

U.S. and South Korean troops on Monday launched major annual land, sea and air exercises, amid North Korean threats to turn Seoul into a "sea of flames" in the event of any provocation.

The Key Resolve/Foal Eagle drills are the first of their type since the communist state's deadly shelling of a South Korean border island last November.

North Korea's military threatened Sunday to fire at South Korea, as Seoul prepared to start annual joint drills with U.S. troops — maneuvers Pyongyang says are a rehearsal for an invasion.

The North's military warned that it would shoot directly at South Korean border towns and destroy them if Seoul continued to allow activists to launch propaganda leaflets toward the communist country, Pyongyang's official Korean Central News Agency said. The warning was conveyed to South Korea's military earlier Sunday, it said.