KUALA LUMPUR (Reuters) - Malaysian Prime Minister Najib Razak on Tuesday called on North Korea to immediately release all its citizens in North Korea, after Pyongyang banned Malaysians from leaving the country in an escalating row over the murder of Kim Jong Nam.

"This abhorrent act, effectively holding our citizens hostage, is in total disregard of all international law and diplomatic norms," Najib said in a statement, adding that he has summoned an emergency meeting of the National Security Council.

Najib said he has also instructed the police "to prevent all North Korean citizens in Malaysia from leaving the country until we are assured of the safety and security of all Malaysians in North Korea".

(Reporting by A. Ananthalakshmi; Editing by Nick Macfie)