WASHINGTON (AP) — A recent satellite image appears to show North Korea is restarting a plutonium reactor, in a move that could raise renewed international alarm over its nuclear weapons program, a U.S. research institute said Wednesday.

The 5 megawatt reactor at the Nyongbyon nuclear facility was shuttered in 2007 under the terms of a disarmament agreement. Pyongyang announced plans in April to restart it amid a litany of threats toward the U.S. and South Korea after it faced tougher international censure over its latest nuclear and rocket tests.