(ATTN: REWRITES first 3 paras; UPDATES with photo, more info in paras 9-21)
SEOUL, March 10 (Yonhap) -- North Korea said Thursday it will nullify all cross-border agreements on economic cooperation and liquidate South Korean assets in the country in response to Seoul's latest sanctions on it.
"From this moment, we declare all the North-South agreements on economic cooperation and exchange null and void," said a spokesman at the committee handling inter-Korean affairs.
The North also said that it will completely sell off all assets owned by South Korean companies in North Korea, pointing to the South's decision to suspend an inter-Korean tour project at Mount Kumgang and to shut down a joint industrial park in the North.
The North's abrupt announcement came as South Korea on Tuesday unveiled a set of its own punitive sanctions against the North over Pyongyang's latest nuclear test and long-range rocket launch.
The measures included banning the entry of vessels that have made a port call in the North and blacklisting key North Korean officials and entities.
The United Nations Security Council last week adopted a new resolution for tougher sanctions, and South Korea took its toughest non-military action in February -- the shutdown of a jointly run industrial complex with the North.
On Feb. 10, South Korea closed the Kaesong Industrial Complex in the North's border city of Kaesong in response to the North's latest provocations.
The day after, North Korea expelled South Koreans remaining in the factory zone and froze assets owned by South Korean firms. The North also designated the Kaesong complex a military-controlled area.
In 2010, North Korea froze and seized South Korean assets at Mount Kumgang after Seoul suspended the tour program there in 2008, following the shooting death of a South Korean tourist.
North Korea also threatened that it is ready to stage "pre-emptive" attacks against South Korea, vowing to deal a "deadly" blow to South Korea.
"We will continuously take the planned special measures for hastening the miserable end of the Park Geun-hye group of traitors by dealing fatal political, military and economic blows to it," the spokesman said.
The North has ratcheted up its belligerent rhetoric as its leader Kim Jong-un has said that his country has made nuclear warheads small enough to be mounted on ballistic missiles. Seoul's defense ministry raised doubts about the North's claims.
Earlier in the day, North Korea fired two short-range missiles into the East Sea in a show of protest against the ongoing annual joint military drills between Seoul and Washington.
"North Korea showed a tit-for-tat response to South Korea over Seoul's move to suspend the factory zone and slap on fresh sanctions," said Kim Yong-hyun, a professor of North Korean studies at Dongguk University.
He said it was a show of strong protest indicating that the North has no intent to seeking exchanges and reconciliation if Seoul does not change.
Last year, South Korea vowed to encourage civic groups to spur exchanges with North Korea in non-political areas such as cultural programs and sports.
But it has suspended civilian inter-Korean exchanges or approval of South Koreans' visits to North Korea since Pyongyang's fourth nuke test on Jan. 6.
Seoul-Pyongyang relations have once again become confrontational after undergoing a short-lived conciliatory mood last year following their rare deal in August on easing military tensions.
Experts said that North Korea will likely immediately kick off the disposal of South Korean assets at the industrial park and facilities at Mount Kumgang on the east coast.
"As the shutdown of the complex has entered into one month, the North announced that it will dispose of South Korean assets at the zone at its will," Kim said.
More than 120 South Korean firms operated factories at the complex, some 50 kilometers northwest of Seoul, employing more than 54,000 North Korean workers to produce labor-intensive goods such as clothes and utensils.
The complex opened in 2004 as a result of the first inter-Korean summit in 2000. It served as a major revenue source for the cash-strapped North, while South Korea benefited from cheap but skilled North Korean labor.
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