South Korea said Wednesday it is closely monitoring North Korea's nuclear activities amid reports the communist country has begun reprocessing spent nuclear fuel to produce plutonium, which can be used to make nuclear weapons.

"The government is watching the relevant movements closely with serious concern," spokesman of Seoul's Unification Ministry, Jeong Joon-hee said during a regular press briefing. 
"They take the spent fuel from the 5 megawatt reactor at Yongbyon and let it cool and then take it to the reprocessing facility, and that's where they've obtained the plutonium for their previous nuclear tests. So they are repeating that process," the official said. 

"It's a well known fact that North Korea has been continuously pursuing various reprocessing activities to secure additional plutonium," the ministry spokesman said. "There has been close coordination between South Korea and the United States on this issue."

Source: QNA