Kim Hjelmgaard

USA TODAY

North Korea and Malaysia barred each other's citizens Tuesday from exiting their respective countries in a tit-for-tat move that comes amid an escalating dispute over the poisoning death of Kim Jong Nam, the North Korean leader’s estranged half brother.

The North’s official Korean Central News Agency said that Pyongyang was banning Malaysians from leaving the country "until the safety of the diplomats and citizens of (North Korea) in Malaysia is fully guaranteed through the fair settlement of the case that occurred in Malaysia."

Malaysia is looking for seven North Korean suspects over Kim's unusual death in a crowded airport terminal in Kuala Lumpur on Feb. 13. Three of them, including an official at the North Korean Embassy, are believed to still be in Malaysia.

Malaysian Prime Minister Najib Razak said the travel ban was tantamount to hostage-taking and said his country would immediately respond in kind by banning North Koreans from leaving Malaysia. "This abhorrent act, effectively holding our citizens hostage, is in total disregard of all international law and diplomatic norms,” Najib said.

Read more:

VX nerve agent used on Kim Jong Nam: 10 milligrams on the skin can kill

Official: Suspect paid $90 to attack Kim Jong Nam

North Korea breaks silence on Kim Jong Nam death, says probe 'full of holes'

Who was Kim Jong Nam, half-brother of N. Korean dictator Kim Jong Un?

Before diplomatic ties disintegrated over the investigation into Kim's death, Malaysia had been one of the few places in the world where North Koreans could travel without a visa. As a result, for years, it’s been a quiet destination for Northerners looking for jobs, schools and business deals.

About 1,000 North Koreans are believed to be working in Malaysia, according to the Associated Press.

Malaysian Deputy Foreign Minister Reezal Marican told reporters at parliament that there are 11 Malaysians in North Korea: Three working at the Malaysian Embassy, two United Nations workers and six family members.

Malaysia has not directly accused North Korea of being behind the attack on Kim, who was killed at the airport with the nerve agent VX, a banned chemical weapon.

Two women, one from Vietnam and one from Indonesia, have been charged with his murder. Both say they were duped into thinking they were playing a harmless prank. They went up behind Kim as he waited for a flight and wiped something across his face.

However, experts say the oily poison was likely made in a sophisticated state weapons laboratory, and North Korea is widely believed to possess large quantities of chemical weapons, including VX.​

North Korea meanwhile has slammed the investigation as biased and demanded Malaysia hand over the body. The North has also refused to acknowledge that the victim is Kim Jong Nam or a relative of its leader, Kim Jong Un. Instead, it refers to him as Kim Chol, the name on the diplomatic passport he was carrying when he died.