The intelligence agency of the Republic of Korea told lawmakers on Tuesday that the Democratic People's Republic of Korea has restarted a plutonium reactor at its main nuclear facility, according to two legislators who attended the closed-door briefing session.

The DPRK said in April it would restart the reactor after tensions ran high following its third nuclear test in February, but it has not confirmed that it has done so. Recent satellite photos have shown signs that the reactor may be operating, The Associated Press reported.

The National Intelligence Service told a parliamentary committee meeting on Tuesday that the DPRK restarted the five-megawatt reactor at its Nyongbyon complex in August but did not say how it obtained the information, according to the office of lawmaker Jung Chung-rae.

"China calls on all parties to maintain calm and restraint and do more things conducive to easing the situation on the peninsula," Foreign Ministry spokeswoman Hua Chunying said on Wednesday.

"Efforts are needed from all parties to achieve the denuclearization of the Korean Peninsula and safeguard the region's peace and stability. Some signs of the defusing of tensions and positive factors have appeared recently, and these signs deserve to be cherished," she said.

Jung's office cited claims from the intelligence agency that the DPRK also conducted long-range missile engine tests at a northwestern site in August and has moved artillery systems closer to the tense border dividing the peninsula, saying they were possible signs of provocation.

Defense officials said the reported engine tests showed the DPRK is continuing to pursue its missile programs but do not mean a launch is imminent. They said they have not detected any signs that Pyongyang's military has done anything suspicious.

The intelligence agency declined to comment on the defense officials' statements.

The DPRK nuclear reactor was shuttered under a now-stalled international aid-for-disarmament deal. The reactor can be weaponized to make atomic bombs. Once it is operating, it can produce about 6 kilograms of plutonium a year, enough for one or two bombs.

The DPRK threatened nuclear wars and issued a string of warlike threats this spring, but has gradually ratcheted down the threats and sought to resume cooperation projects with the ROK and stalled six-party disarmament talks.

Earlier on Tuesday, the DPRK's military said its troops had been given an "emergency order" to re-examine operational plans and be ready to launch them to cope with planned trilateral maritime drills by the ROK, the US and Japan this week. ROK and US officials said the drills in international seas off a southern ROK island are routine training aimed only at improving readiness to respond to maritime disasters.

Chin Hee-gwan, a Korean studies expert at the Inje University, said the DPRK's latest threat shows its frustration at the lack of progress over its push to resume the lucrative cooperation projects with the ROK and the Six-Party Talks. He said Tuesday's threat wasn't as serious as those it issued earlier this year and the DPRK isn't expected to raise tensions again anytime soon as it has to focus on reviving its economy.

The Korean Peninsula officially remains at a state of war because the 1950-53 Korean War ended with an armistice, not a peace treaty. About 28,500 US troops are stationed in the ROK.

AP-Xinhua-China Daily