Seoul, Bloomberg—North Korea restarted its Yongbyon nuclear reactor, a South Korean lawmaker said, as the North put its troops on high alert and said it’s “ready to confront” the US and the South over naval drills set for this week.

The National Intelligence Service informed lawmakers of the restart, ruling New Frontier Party lawmaker Cho Won Jin said by phone yesterday. Lawmakers were also told that North Korean leader Kim Jong Un told his cabinet he plans to seek reunification with the South by force in three years, Cho said.

Running the reactor at Yongbyon would mean the North is making good on promises made in April to restart the facility as part of efforts to produce energy and improve its nuclear armed force. The United Nations Security Council has imposed strict sanctions on the North in a bid for it to return to negotiations and abandon its nuclear ambitions.

The finding backed up satellite-imagery analysis this month that indicated the North resumed nuclear activity there. The imagery from last month showed water being released into the Kuryong River from the reactor facility at North Korea’s main nuclear complex, according to the 38 North website, run by the US-Korea Institute at Johns Hopkins University’s School of Advanced International Studies in Washington.

A spokeswoman at the intelligence service who asked not to be named declined to comment on Cho’s remarks. The reactor was mothballed under a six-nation disarmament deal in 2007.

Tensions on the peninsula have heightened since February, when North Korea tested its third nuclear device and then threatened first strikes against the US and South Korea over UN sanctions imposed after the February 12 blast.

In a statement carried on its official Korean Central News Agency yesterday, the North warned of possible “tragic situations” that may result from the military drills set for this week. The maneuvers, which will include forces from Japan, aim to better coordinate disaster response.

“The US will be entirely accountable for tragic situations to be brought by the nuclear-armed invaders from the US,” an unidentified official with the Korean People’s Army said in the statement. “The US should know that our army is ready to confidently confront whatever turbulences and perilous provocations with powerful military forces.”

A typhoon moving through the region led the US and South Korea to suspended the drills yesterday and today, South Korean Defense Ministry spokesman Kim Min Seok said at a briefing in Seoul. South Korea’s military is closely monitoring the North’s troop movements, Kim said.

The USS George Washington Strike Group has arrived in South Korea from its base in Yokosuka, Japan to participate in the exercises. The nuclear-powered George Washington carries 75 planes, according to the US Navy.

North and South Korea remain divided along one of the world’s most fortified borders 60 years after the Korean War ended in a stalemate. North Korea regularly threatens the South, though actual combat between the two sides has been rare since the end of the war.

The exercises come a week after the US and South Korea signed a new joint-defense strategy that would allow for first strikes against North Korea to counter any possible threat of nuclear attack. The agreement affirmed a US commitment to use “the full range of military capabilities” to deter any North Korean attack, the two governments said in a joint communique after the October 2 signing.