A week ago special services of North Korea confiscated all the mobiles from local enterprises and individuals.
Mobiles are expensive in Korea ($300-500), but the authorities did not refund the people the cost of the phones.
At the same time, foreigners being in North Korea have been allowed to purchase and use mobile phones, but the cost of this service is expensive: about $2,000.
According to the sources, North Korean authorities banned mobiles for the country citizens to restrict their communications with foreigners. It was hard for North Korean special services to overhear all conversations as more and more people were using mobiles.