(CNN) -- North Korea will not allow Malaysian nationals inside its country to leave, marking a new low in the diplomatic row over the murder of Kim Jong Nam.
Eleven Malaysians are believed to be in North Korea, a Malaysian government official told CNN, including four embassy staff and their families and two from United Nations.
"This abhorrent act, effectively holding our citizens hostage, is in total disregard of all international law and diplomatic norms," Malaysian Prime Minister Najib Razak said in a statement Tuesday.
Malaysia retaliated by barring all North Korean citizens from leaving Malaysia "until we are assured of the safety and security of all Malaysians in North Korea," Razak said.
Three North Korean nationals wanted for questioning over the murder of Kim Jong Nam, North Korean leader Kim Jong Un's half-brother, are believed to be holed up in the Malaysian embassy in Kuala Lumpur, Malaysian police revealed Tuesday.
They include Hyon Kwang Song, the embassy's second secretary, and Kim Uk Il, a staff member at North Korea's national carrier Air Koryo. Police issued an arrest warrant for Kim last week.
"It is a matter of time before they come out," Royal Malaysia Police Inspector-General Khalid Abu Bakar said. "We will wait. If it takes five years, we will wait outside."
Pictures outside the embassy appeared to show a police presence gathering.
Murdered at the airport
Kim Jong Nam was killed last month at Kuala Lumpur International Airport after being poisoned by VX, a deadly nerve agent, according to Malaysian authorities.
South Korea is the only country that has blamed North Korea for assassinating Kim, a claim Pyongyang has strongly denied.
However, relations between Malaysia and North Korea have deteriorated over the course of the investigation.
Both countries have expelled their respective ambassadors, but North Korea's move to bar Malaysians from leaving warranted a retaliatory response, Malaysia's deputy leader said.
"This is what needs to be done when a country that has diplomatic relations with Malaysia does something that is beyond diplomatic norms and etiquette and Malaysia is forced to take action," said Deputy Prime Minister Ahmad Zahid Hamidi.
"We want to send a clear message to North Korea not to point fingers at Malaysia, and don't belittle the status of Malaysia as a sovereign country."
Two women have been charged with Kim's murder and face the death penalty if convicted: Siti Aisyah from Indonesia and Doan Thi Huong from Vietnam.
Malaysian authorities believe the two women were recruited by the North Koreans to kill Kim Jong Nam on February 13 before he was set to catch a flight from Kuala Lumpur to the Chinese-controlled territory of Macau.
Police say they wiped his face with VX, which killed him in under 20 minutes.
Authorities from both countries said the women believed they were participating in a prank TV show, but Malaysian authorities believe the women knew what they were doing.
Police have requested Interpol assistance in finding four other North Korean suspects who are believed to be back in Pyongyang.
CNN's Marc Lourdes and Zahra Ullah and journalist Danny Lim contributed to this report
™ & © 2017 Cable News Network, Inc., a Time Warner Company. All rights reserved.