South Korea’s intelligence chief told the parliament Tuesday that North Korea restarted its nuclear reactor capable of producing weapons-grade plutonium in August, ruling party lawmakers said.

National Intelligence Service Director Nam Jae-joon was also quoted as saying that the North tested a long-range rocket engine around that time and recently beefed up naval forces and artillery near the border.

“North Korea has restarted the 5-megawatt reactor to boost its nuclear capabilities,” Nam told the National Assembly Intelligence Committee, according to lawmakers Cho Won-jin of the ruling Saenuri Party and Jung Cheong-rae of the main opposition Democratic Party.

“North Korea is seeking to secure status as a nuclear state and gain an upper hand in the Korean Peninsula situation through an unconditional resumption of the six-party talks,” he was quoted as saying.

He was confirming recent satellite imagery analyses by a U.S. think tank that Pyongyang has restarted the graphite-moderated reactor in Yongbyon that was closed in 2007 under a denuclearization agreement.

Early this month the U.S.-Korea Institute at Johns Hopkins School of Advanced International Studies said a Sept. 19 satellite image showed hot water being released through a drainpipe that is part of a cooling system for the reactor.

Pyongyang in April threatened to resume operation of the facility amid heightening tension.

On Sept. 23, the institute said satellite photos taken in late August suggested North Korea tested a long-range rocket engine which may be the second stage of the Unha-3 Space Launch Vehicle or the second or third stage engine of a much larger rocket under development.

The spy chief also said the military-focused regime has been beefing up naval forces and artillery units targeting the Seoul metropolitan area and border islands in the West Sea, deploying 240- and 122-milimeter multiple rocket launchers.

North Korean leader Kim Jong-un has “frequently avowed to reunify the Korean Peninsula by force within three years,” he added.

Nam also unveiled an intelligence report that Kim has replaced some 44 percent of military officers of the level of corps commander or higher.

Earlier in the day, state media said the North placed its troops on an emergency posture in protest against joint drills here by South Korea, the U.S. and Japan which involved a nuclear-powered aircraft carrier.

The General Staff of the Korean People’s Army lambasted the deployment of the USS George Washington in the East Sea, which arrived in Busan on Sept. 30 for four-day Seoul-Washington maritime exercises and trilateral programs with Tokyo scheduled for Oct. 8-10.

The latter drills were delayed due to bad weather. It was initially expected to include the guided-missile USS Antietam CG-54 cruiser, USS Preble DDG 88 destroyer, fighter jets, anti-submarine helicopters and early warning aircraft.

“Now the U.S. imperialists are openly advertising that the drills to be staged with the aircraft carrier task force as an axis are a planned military offensive to pressurize the DPRK (North Korea) in a bid to deter its possible ‘provocations’ including nuclear test and missile launch and lead it to ‘changes’ desired by them,” said the military organ’s spokesman in a statement carried by the Korean Central News Agency.

It claimed the 97,000-ton supercarrier is equipped with at least 100 nuclear bombs, guided-missile destroyers, cruisers, submarines and escort warships, among others.

As a result, the KPA’s supreme command on Saturday ordered all troops to reexamine already-ratified operation plans and “keep themselves fully ready to promptly launch operations any time, watching with high vigilance every move of the U.S. and Japanese aggressors and the (South Korean) puppet forces,” the statement said.

“The U.S. should bear in mind that the more frequently and the deeper its imperialist aggression forces’ nuclear strike means including the nuclear carrier enter the air above the vicinity of the Korean Peninsula and waters off it, the more unpredictable disasters their actions will cause.”

The announcement again raised tension on the peninsula that has in recent months witnessed a thaw in cross-border ties after a string of Pyongyang’s warlike threats early this year.

The heavily-militarized country has routinely accused the allies of staging joint drills as a dress rehearsal for war. In March, the North threatened nuclear strikes on Seoul and the U.S. after they conducted annual trainings involving bombers, stealth jets and aircraft carriers.

Last week, the communist state also warned the U.S. of “disastrous consequences” of the naval exercises, putting its troops on alert.

It also harshly criticized President Park Geun-hye by name last week and vowed to stick to its parallel pursuit of nuclear and economic development.

The moves are seen as an attempt to press Washington to return to the negotiating table as Pyongyang has called for high-level dialogue with the U.S. and a restart of the six-nation denuclearization talks that have been on hold for five years.

But Seoul and Washington remain unwavering in their demand that Pyongyang should first prove its sincerity with action.

The South said Pyongyang’s anti-Seoul rhetoric is “going too far,” urging the regime to stop threatening the South Korean citizens and humiliating the president.

“North Korea may think that it could draw attention of our people and the international community through provocative words,” the Unification Ministry said in a statement.

“In fact, it must realize as early as possible that all it could get is nothing but international isolation.”

The Defense Ministry said it is closely watching the North Korean military’s moves.

“The North Korean military’s emergency posture is presumably designed to respond to the U.S. aircraft carrier’s entry,” ministry spokesman Kim Min-seok told reporters. “We are prepared to sternly counter any North Korean provocation.”

By Shin Hyon-hee (heeshin@heraldcorp.com)