PETALING JAYA (THE STAR/ASIA NEWS NETWORK) - North Korean workers overseas have been banned by their government from accessing the Internet via smartphones to prevent the spread of news on the assassination of Kim Jong Nam, reported broadcaster Radio Free Asia.

"North Korea has ordered its overseas missions to forbid its workers dispatched abroad not to access the Internet via smartphones, with a warning of their recall and punishment (if they) disobey the order," Radio Free Asia said, citing a source in Vladivostok, Russia.

Officials at the missions were also prohibited from accessing the Internet, according to the source.

Kim, the half-brother of North Korean leader Kim Jong Un, was killed at the Kuala Lumpur International Airport 2 departure hall on Feb 13, with what Malaysian police said was the banned VX nerve agent.

"Do not access the Net, do not spread any kind of news … a summons and severe punishment will be made when violating the order," the order read, according to the source.

The source added that there have been random inspections of the smartphones of overseas labourers since the order was issued.

Another source in Vladivostok also said that officials at North Korean missions recently assembled their workers to convey the instruction to them.

"The ban apparently has something to do with the rapid spread of the news on Jong Nam's murder inside the North," the source said.

On March 1, Vietnamese Doan Thi Huong and Indonesian Siti Aisyah were charged with Kim's murder under Section 302 of the Penal Code that carries the mandatory death penalty upon conviction.

Neither recorded a plea, and April 13 has been fixed for mention.

Four other North Korean suspects, believed to have been the masterminds behind the murder, have left the country.

North Korea has criticised Malaysia's handling of the case and on Tuesday announced its decision to temporarily ban Malaysians in North Korea from leaving the country.

A few hours after Pyongyang's announcement, Prime Minster Datuk Seri Najib Tun Razak announced that all North Koreans in Malaysia would not be allowed to leave.