North Korea may be preparing to conduct nuclear tests

Activists wear the face masks of North Korean leader Kim Jong-Un and his wife Ri Sol-Ju (bottom C) as they " title="North korea nuclear tests" itemProp="contentUrl" />

Activists wear the face masks of North Korean leader Kim Jong-Un and his wife Ri Sol-Ju (bottom C) as they "beg" for money during an anti-Pyongyang rally urging North Korea to abandon nuclear weapons in Seoul on January 31. South Korean President Lee Myung-Bak held an emergency security meeting on Jaunary 31 that warned North Korea of "serious consequences" if it went through with an expected nuclear test.

There was increased speculation today that North Korea might be preparing for nuclear tests, after satellite images and intelligence reports hinted at increased activity near nuclear test sites.

North Korean leader Kim Jong Un "made an important decision that will serve as a guiding principle in defending the country's security and sovereignty," the North's official KCNA news agency reported on Sunday, according to South Korean newspaper Chosun Ilbo.

On Jan. 31, South Korean media reported that Kim Jong Un had issued martial law in the North and declared that a nuclear test would take place sometime between last week and this Tuesday.

Following revelations that the North Korean military is covering up one tunnel to prevent satellite observation, GlobalPost senior correspondent Geoffrey Cain reports that "there's activity at a second site at Punggye-ri, the purported nuclear test area."

"They've concluded that North Korea could, therefore, be getting ready to detonate two bombs at the same time or back-to-back, perhaps to demonstrate their power," Cain reported from Seoul.

If the allegation turns out true, it would be significant. This signifies that the pariah state is not using highly enriched uranium, as was discovered early last year, but that it's gone so far to produce two pretty sophisticated, expensive bombs when you consider its level of poverty.

Chosun Ilbo quoted a military official as saying, "There is a chance that the southern tunnel is a decoy, but we are not ruling out that the regime will conduct nuclear tests simultaneously at both tunnels," according to The Daily Telegraph.

Yu Woo-ik, South Korea's unification minister, said the North is likely to carry out what would be its third round of nuclear testing, though he gave no time-frame.

"If the North Korea nuclear test takes place, it is a provocation against the international community. This is a major provocation against South Korea," said Kim Min-seok, a spokesman for the defense ministry, according to Al Jazeera.

US Secretary of State John Kerry, Japanese Foreign Minister Fumio Kishida and South Korea's Kim Sung-hwan reportedly held a round of calls on Sunday, agreeing that North Korea must understand "that it will face significant consequences from the international community if it continues its provocative behavior," according to a State Department of the calls obtained by CNN.

South Korean UN Ambassador Kim Sook said on Monday that the UN Security Council is united on the issue and will take tough measures against Pyongyang if the tests are carried out.

"The North Korean nuclear test seems to be imminent," said Kim, who is serving as president of the Security Council this month.

"Everybody is unified and they are firm and resolute," he said, according to Reuters. "I would expect very firm and strong measures to be taken ... once they go ahead with such provocation."

More on GlobalPost: North Korea decrees martial law amid nuclear testing rumors

Geoffrey Cain contributed to this report from Seoul.