North Korea has apparently intensified a crackdown to stem an increasing exodus of its people by picking up defectors who work along the border to help others escape. Experts say that the North seems to have started the crackdown around November last year.

Lee Jo-won, a professor at Chungang University, said, "There is a likelihood that U Dong-chuk, the senior deputy director of the State Security Department, and Ju Sang-song, the minister of Public Security, had discussions with Chinese officials over the defector issue when they visited China late last year. Defectors should be very careful when they go to China."

Three or four defectors who settled in South Korea have been out of contact recently after they went to China. A defector who supplied information on the North to a radio station has been out of contact for two months since he went to meet his North Korean source there.

The North Korean regime sent instructions to regional security agencies in early March to "thoroughly punish national traitors, including defectors."

Since then, there have been concerted efforts in the North to ferret out and crack down on residents who have maintained links with the outside world. Defectors' families who lived near the border area have been relocated to inland areas, and people who had been caught talking with the outside by phone three or four years earlier were reportedly investigated again.

In a statement on March 23, the North's Korean Council for Reconciliation and Cooperation, an agency for South Korean affairs, listed defectors' organizations in South Korea which broadcast North Korea news. It threatened that they would become "primary targets for punishment."

Kim Sung-min, the president of Free North Korea Radio, said, "It has become very difficult to talk with our sources in the North recently."

The North seems to believe that defectors' activities could undermine the regime. Defectors' news media are broadcasting inside news on the North nearly in real time thanks to the spread of mobile phones in the North.

They reported on the North's botched currency reform late last year faster than the National Intelligence Service. The number of defectors living in South Korea is expected to exceed 20,000, while up to 50,000 are believed to be in China and other countries.