A plant for reprocessing plutonium for use in nuclear weapons in North Korea may have been reopened, the UN's International Atomic Energy Agency (IAEA) announced on Monday.

"There are indications the reprocessing plant at Yongbyong has been reactivated," IAEA spokesman Fredrik Dahl said.

Since the IAEA is not allowed to inspect North Korea's nuclear sites after being kicked out of the country in 2009, agency head Yukiya Amano cautioned: "We are only observing through satellite imagery. We cannot say for sure."

However, the satellite data at the main Yongbyon complex (pictured above) depicted the "resumption of the activities of the 5 megawatt reactor, the expansion of centrifuge-related facility" as well as the "movement of vehicles, steam, discharge of warm waters or transport of material."

Centrifuges enrich uranium, a process that can purify the element to the level needed for use in a nuclear weapon. Reprocessing involves obtaining plutonium from spent reactor fuel, another option in the creation of bombs.

Back in February, the director of US National Intelligence, James Clapper, warned that North Korea could begin recovering plutonium from the Yongbyon reactor "within a matter of weeks to months."

North Korea conducted its latest nuclear test explosion in January, the country's fourth since 2006. Following the test, the isolated nation came under international pressure, including tougher UN sanctions which were adopted in March and backed by the North's major ally China.

The UN Security Council recently condemned the North's failed missile launch in May.

rs/bw (AFP, dpa, Reuters)