Pyongyang blamed South Korea Thursday for the death of the half-brother of North Korean leader Kim Jong Un, who was killed in a Malaysian airport, the South Korean Yonhap News Agency reported.

Kim Jong Nam, traveling under the name Kim Chol, was poisoned at Kuala Lumpur International Airport on Feb. 13 as he waited for a flight to Macau. A woman reportedly sprayed a fast-acting poison at him and a second woman grabbed him from behind and covered his face. He died en route to a hospital.

It is widely believed North Korea was behind the attack.

The North Korean embassy accused Malaysia of siding with South Korea and infringing on the North’s international rights after Malaysian officials rejected Pyongyang’s demand for a joint investigation.

Malaysian authorities are holding three suspects in the case, a Vietnamese woman, an Indonesian woman and a North Korean man. Malaysian police said they also were questioning a senior official at the North Korean embassy and a staffer at its state airline, Free Malaysia Today reported. Four other male suspects, all North Korean, reportedly have fled the country. The New York Times said three others are being sought.

North Korea demanded the suspects be released immediately, saying they had been “arrested unreasonably.” It also objected to investigators taking the word of South Korean officials about the victim’s identity.

“The action of requesting for the presence of the victim’s next of kin for the purpose of identification and a DNA test took no regard of our confirmation of the identity of the deceased DPRK [Democratic People Republic of Korea] citizen,” the embassy said in a statement.

Malaysian authorities are refusing to release the body without the presence of next of kin.

Inspector-General of Police Khalid Abu Bakar said Wednesday the female suspects washed their hands after the attack, indicating they knew they were dealing with a toxic substance and not just committing a prank.

But the embassy argued: “This means that the liquid they daubed for a joke is not a poison and that there is another cause of death.”