Malaysian police investigating what US and South Korean officials say was an assassination carried out by North Korean agents took statements from the three North Koreans before they were allowed to leave the country.
"We have obtained whatever we want from them... They have assisted us and they have been allowed to leave," police chief Khalid Abu Bakar told a news conference in Kuala Lumpur, saying there was no grounds to hold the men.
Kim Jong Nam, the elder half-brother of the North's young, unpredictable leader Kim Jong Un, was killed at Kuala Lumpur's airport on Feb. 13 in a bizarre assassination using VX nerve agent, a chemical so lethal that it is on a U.N. list of weapons of mass destruction.
China's Foreign Ministry spokesman Lu Kang said the remains of a North Korean citizen killed in Malaysia were returned to North Korea via Beijing along with "relevant" North Korean citizens.
Malaysian authorities released Kim's body on Thursday in a deal that secured the release of nine Malaysian citizens held in Pyongyang after a drawn out diplomatic spat.
Malaysian police had named eight North Koreans they wanted to question in the case, including the three who were given safe passage to leave Malaysia on Thursday evening.
Television footage obtained by Reuters from Japanese media showed Hyon Kwang Song, the second secretary at the North Korean embassy in Kuala Lumpur, and Kim Uk Il, a North Korean state airline employee on the flight from Kuala Lumpur to Beijing.
The police chief confirmed they were accompanied by compatriot Ri Ji U, also known as James, who had been hiding with them at the North Korean embassy in Kuala Lumpur.
Malaysian prosecutors have charged two women - an Indonesian and a Vietnamese - with killing him, but South Korean and U.S. officials had regarded them as pawns in an operation carried out by North Korean agents.
Kim Jong Nam, who had been living in exile in the Chinese territory of Macau for several years, survived an attempt on his life in 2012, according to South Korean lawmakers.
They say Kim Jong Un had issued a "standing order" for his assassination to consolidate his own power following their father's death in 2011.
The other North Koreans named by Malaysian investigators are all back in North Korea.
Police believe four fled Malaysia on the same day as the murder and another was held for a week before being released due to insufficient evidence.
Angered by the probe, North Korea issued a travel ban on Malaysians earlier this month, trapping three diplomats and six family members - including four children - in Pyongyang.
Malaysia, which had previously friendly ties with the unpredictable nuclear-armed state, responded with a ban of its own, but was left with little option but to accede to North Korea's demands for the return of the body and safe passage for the three nationals hiding in the embassy.
Malaysian Prime Minister Najib Razak , who is currently on an official visit in India, issued a statement announcing the return of the body, but did not mention Kim by name.
"Following the completion of the autopsy on the deceased and receipt of a letter from his family requesting the remains be returned to North Korea, the coroner has approved the release of the body," Najib said, adding that the murder investigation would continue but the travel ban on North Koreas was lifted.
North Korea has maintained that the dead man is not Kim Jong Nam and that the body is that of Kim Chol, the name given in a passport found on the victim.
Using a DNA sample, Malaysian police have established that the victim was Kim Jong Nam. Police chief Khalid said the North Korean embassy had at first confirmed that the dead man was Kim Jong Nam, but changed its mind the next day.
The swap agreement brings to an end a diplomatic standoff that has lasted nearly seven weeks.
A North Korean statement on Thursday said both countries managed to "resolve issues arising from the death of a DPRK national."
"It is a win (for North Korea), clearly," Andrei Lankov, North Korea expert at Seoul's Kookmin University said on the swap deal. "I presume the Malaysians decided not to get too involved in a remote country's palace intrigues, and wanted their hostages back."
The nine Malaysians who had been trapped in Pyongyang arrived in Kuala Lumpur early Friday morning on board a small Bombardier business jet operated by the Malaysian air force.
Pilot Hasrizan Kamis said the crew dressed in civilian clothes as a "precautionary step" for the mission.
According to the Plane Finder tracking website the Bombardier took off from Pyongyang at the same time that the Malaysian Airlines flight MH360 left Kuala Lumpur for Beijing.
Mohd Nor Azrin Md Zain, one of the returning diplomats, said it had been an anxious period but they "were not particularly harassed" by the North Korean authorities.
The episode, however, is likely to have cost North Korea one of its few friends.
"I think this relationship is going to go into cold storage for a very long time," said Dennis Ignatius, a former Malaysian diplomat.