As expected, many factors strongly suggest that North Korea was behind the vicious killing of Kim Jong-nam, the half brother of North Korean leader Kim Jong-un. This leaves Malaysia and the world with a responsibility for action.

First and foremost, Malaysian authorities should investigate the premeditated killing thoroughly. The case is drawing international attention because the victim is the estranged brother of the leader of the reclusive, totalitarian country, but any such apparent terrorist attack -- whoever the victim may be -- should not be condoned.

The most urgent work for Malaysian authorities is to trace the activities of five suspects -- all identified as North Korean nationals -- who had been near the scene of the attack committed by a Vietnamese woman and an Indonesian woman at Kuala Lumpur International Airport on Feb. 13.

Only one of the five are in custody, with Malaysian police saying the remaining four North Koreans, who had entered Malaysia separately, left the country shortly after the attack through the same airport. Local news reports said they have already returned to Pyongyang via third countries.

Officials said the detained man, Ri Jong-chol, 46, was in possession of an identification card the Malaysian government issues for registered foreign workers.

The fact that five North Korean men, including one who had been staying in Kuala Lumpur with his family, were involved in the case suggests that Pyongyang was behind the killing of the eldest son of late North Korean leader Kim Jong-il.

Malaysian authorities should work closely with Interpol and relevant countries to find out the truth of the inhumane act of terrorism. Questioning of Ri is also crucial in finding out who was involved in the attack and how they drew the two foreign women into the work.

Malaysian authorities are right to reject the North Korean Embassy’s demand that Kim’s body be handed over to its side. Its ambassador, Kang Chol, also criticized Malaysian authorities for conducting an autopsy without the presence of its officials.

It is little surprise that North Korean officials make such irrational demands, but they clearly defy international norms and laws. As Malaysian officials noted, Kim’s family members have priority in claiming his body. They should stick to that position and not hand over the body, at least not before finding out the exact cause of death.

The apparent North Korean-ordered killing of Kim offers challenges to South Korea and other members of the international community as well.

The incident proved once again the world is dealing with a regime led by a ruthless, impulsive young dictator who does not spare even his siblings and relatives from executions, assassinations, purges and torture.

That should prompt the international community to raise its voice for a regime change in Pyongyang. Since Donald Trump took office as US president, notions of a new approach, like a regime change, secondary boycotts and even pre-emptive or preventive strikes are gaining momentum regarding the North’s nuclear and missile programs.

Another step the international community could take is sending case of Kim’s murder to the International Criminal Court, where a South Korean activist group had already submitted a petition to look into the brutal execution in 2013 of Kim Jong-un’s uncle, Jang Song-thaek, and other charges of genocide.

The attack on Kim is an apparent act of terrorism. It should therefore revive talk in the US of putting North Korea back on its list of state sponsors of terrorism.

North Korea was included on the US terrorism sponsor list for the 1987 midair bombing of a Korean Airlines flight that killed all 115 people aboard. The George W. Bush administration removed Pyongyang from the list in 2008 in line with progress in denuclearization talks.

US congressman Ted Poe, a Republican from Texas who serves as chairman of the House of Representative’s subcommittee on terrorism and trade, said that if Kim’s killing is confirmed as an act committed by the North, the US should consider putting it on the list again. The proposal deserves strong support.