North Korea has started a drive to confiscate mobile phones smuggled from China in an attempt to suppress news from the outside world, a group of defectors from the communist state said.

North Korea Intellectuals Solidarity said in its latest newsletter police in North Hamkyong and Yangkang provinces bordering Russia and China have started urging residents to voluntarily surrender mobile phones or face punishment.

It cited sources in the border cities of Hyesan and Hoeryong.

The police warned that special devices to detect mobile phone use had been brought in to punish "those spreading capitalist ideas and eroding socialism", the group quoted one of the sources as saying.

North Korea strictly controls access to outside information and fixes the tuning controls of radios and televisions to official stations.

But many residents in border areas that can receive mobile reception from China are known to use smuggled phones to talk to relatives and friends who escaped the impoverished state to settle in China or South Korea.

At present users restrict conversations to five minutes, the minimum time authorities need to trace a call, said the source.

South Korean analysts and officials say the reclusive regime has lately tightened controls on outside information to suppress news of popular revolts against despots in the Arab world.

There is no hard data on the number of mobile phones smuggled from China.

But more than 5,000 people in Hyesan alone had used smuggled mobile phones as of 2006, Do Myourng-Hak, a group spokesman who defected that year, told AFP.

The North also has a legal mobile phone service provided by Egypt's Orascom Telecom. But activists say it is difficult for registered users to make or receive overseas calls because of limited service and tight oversight.