The U.N. special rapporteur on North Korea said Monday the recent murder in Malaysia of Kim Jong Nam, the estranged half-brother of North Korea’s leader, could amount to an extrajudicial killing, which would open the door to international investigation.

“Should the investigation confirm the involvement of state actors, Mr. Kim would be a victim of an extrajudicial killing and measures would need to be taken to assign responsibilities,” Tomas Ojea Quintana said during a session of the U.N. Human Rights Council.

Malaysian authorities suspect North Korea orchestrated the assassination of Kim Jong Un’s half-brother, who is known to have criticized the country’s hereditary succession, at Kuala Lumpur International Airport on Feb. 13, using the highly toxic nerve agent VX. North Korea claims the man died from a heart attack.

“I plan to request official information on the outcome of the investigation, in order to understand where the investigation is going, to what extent the investigation shows the involvement of state actors, and if that is the case, what state actors are involved,” Quintana said in an interview.

“Then, I will be able to address the issue from a human rights point of view,” he added.

Quintana, who succeeded Marzuki Darusman of Indonesia as special rapporteur on the country in August 2016, is following a two-track approach combining engagement with North Korean authorities and a push for accountability on human rights violations.

His engagement strategy has shown mixed results so far, leading to only limited contact with North Korean diplomatic representatives.

The North Korean delegation boycotted the Human Rights Council session on Monday, which was dedicated to human rights violations committed by the reclusive regime.

Quintana pointed to the centrality of China in addressing the North Korean issue in lieu of direct contact with Pyongyang.

“I think China is very important, not only in respect to the security question, but also on the human rights issue,” Quintana said, while regretting the “reluctance” of Chinese officials to engage on human rights matters.

On the accountability track, U.N. High Commissioner for Human Rights Zeid Ra’ad Al Hussein named last year Sonja Biserko of Serbia and Sara Hossain of Bangladesh as part of a team to seek accountability for human rights violations in the isolated country.

The two legal experts work closely with Quintana and have recently visited Geneva, The Hague, Seoul, Tokyo and New York to consult with various stakeholders, including scholars of international criminal justice and persons who left North Korea in 2016.

“We call on the international community to continue to pursue a referral of the situation in the DPRK to the International Criminal Court,” Hossain said during the Human Rights Council session.

Hossain used the acronym for the Democratic People’s Republic of Korea, the official name of the country.

“There should be very serious examination of what questions can go before the International Criminal Court, in respect to which perpetrators and which violations,” Hossain said, while recognizing this remains a matter of political will among members of the U.N. Security Council.

A U.N. commission investigating human rights violations in North Korea suggested in a report released in February 2014 that top government officials — among them leader Kim Jong Un — could be held responsible for crimes against humanity.

Quintana also touched on the issue of Japanese nationals abducted by North Korea during the 1970s and 1980s, saying to the Human Rights Council he was “committed to using all possible avenues to access accurate and reliable information on people who were abducted or went missing.”

On the other hand, Quintana raised doubts about the efficacy of the Japanese government’s policy toward North Korea.

“I understand how serious it is to see missiles going into the exclusive economic zone, but at the same time reacting with unilateral sanctions leads the DPRK to close any discussion on the abductees,” Quintana said, referring to a recent multiple-missile salvo from North Korea.