SEOUL — Pyongyang is banning all Malaysian citizens from leaving North Korea, state media said on Tuesday, potentially holding them hostage amid an increasingly heated diplomatic row over the killing of a North Korean said to be Kim Jong-Nam, the half-brother of Pyongyang’s leader, in Kuala Lumpur.

"All Malaysian nationals in the DPRK will be temporarily prohibited from leaving the country until the incident that happened in Malaysia is properly solved," the official Korea Central News Agency said, citing the foreign ministry.

Meanwhile, North Korea’s expelled ambassador fired a final verbal salvo at Malaysia on Monday over its investigation into the assassination of Kim Jong-Nam, describing the probe as biased.

Speaking at Kuala Lumpur International Airport before his flight left, ambassador Kang Chol lashed what he called a "pretargeted investigation by the Malaysian police".

The murder of a man believed to be Kim Jong-Nam with VX nerve agent at the same airport last month sparked an acrimonious dispute between the two countries.

North Korea retaliated late Monday by ordering Malaysia’s ambassador to Pyongyang to leave within 48 hours, the North’s official media reported.

The diplomat had already been withdrawn by Kuala Lumpur for consultations.

In Kuala Lumpur, Malaysia’s foreign ministry confirmed its ambassador to Pyongyang had been officially declared persona non grata.

"This reciprocal action is normal in diplomacy," said ministry director-general Raja Nurshirwan.

North Korea has not acknowledged the dead man’s identity but has repeatedly criticised the murder investigation and autopsy, accusing Malaysia of conniving with its enemies.

"They have conducted the autopsy without the consent and attendance of the DPRK (North Korea) embassy and later arrested a DPRK citizen without any clear evidence showing his involvement in the incident," ambassador Kang said.

In a sign of the security tensions, police armed with assault rifles cordoned off the entrance to North Korea’s embassy in Kuala Lumpur before the envoy left.

Kang departed in a black chauffeured Jaguar -- the North Korean flag which denotes an ambassador was removed from its bonnet.

He checked in a Philips TV, three suitcases and four boxes vacuum-wrapped and marked with the words "DPRK Pyongyang".

Senior government officials said he left at 6.25 pm (1025 GMT) on flight MH360 for Beijing, shortly after the deadline for his expulsion at 6 pm.

He landed in the Chinese capital in the early hours of Tuesday morning, leaving the airport via a VIP exit surrounded by security, AFP journalists at the scene said.

He was then whisked away in a North Korean diplomatic car to Pyongyang’s vast embassy complex in central Beijing, where he was expected to spend the night before flying on to North Korea. — AFP