Photo/IllutrationA diplomatic vehicle thought to be from the North Korean Embassy arrives Feb. 14 at a medical facility in Kuala Lumpur where the autopsy on Kim Jong Nam is believed to have been performed. (Masanobu Furuya)

Kim Jong Nam, the murdered half-brother of North Korean leader Kim Jong Un, had good reason to fear for his safety as an attempt was made on his life in Beijing as early as 2012, sources said.

South Korean intelligence officials believe that the fatal poisoning of Kim Jong Nam in the concourse of busy Kuala Lumpur International Airport on Feb. 13 was the work of agents working on behalf of the North Korean government.

Sources close to the Chinese government disclosed that a North Korean hit squad went after Kim Jong Nam in 2012 in Beijing, but that the attempt was thwarted by Chinese police as the eldest son of late North Korean leader Kim Jong Il was under China's protection.

South Korean intelligence officials noted that a "standing order" went out from about 2012 after Kim Jong Un took over upon the death of his father to have his estranged sibling killed.

Kim Jong Nam, who was in his mid-40s, was well aware that his brother was gunning for him and had no qualms about ordering his death if the opportunity presented itself.

A former high-ranking U.S. government official, citing a highly placed source in the Chinese government, referred to an incident in China that came to nothing because the hit squad members dispatched from North Korea were detained and sent back to North Korea.

Officials of South Korea's National Intelligence Service blame Kim Jong Un's paranoia for the persistent attempts to do away with Kim Jong Nam even though he had no political power base to speak of to even pose any real threat to the reclusive regime in Pyongyang.

Kim Jong Un was intent on eliminating even the smallest possibility of a threat, however.

About the only claim to power that Kim Jong Nam had was being the son of Kim Jong Il, and that apparently was sufficient to ensure that the standing order to kill Kim Jong Nam was not lifted.

North Korea may have chosen Malaysia to carry out the hit because the Southeast Asian country's relatively relaxed security measures make it fertile ground for its agents to act with impunity.

Kim Jong Nam was planning to fly from Malaysia to Macao, where he and his family lived under China's protection. China is a long-standing ally of North Korea, and the only significant country to maintain friendly relations with the regime, despite hiccups over the North's nuclear posturing.

A former South Korean government official said China began looking out for Kim Jong Nam through Beijing's close ties with Jang Song Thaek, the uncle of Kim Jong Nam who was executed by firing squad in December 2013. Jang was considered a mentor of sorts to Kim Jong Nam and effectively held the No. 2 spot in the Pyongyang hierarchy before his downfall.

Beijing kept a close eye on Kim Jong Nam for pragmatic reasons, according to the former South Korean government official.

"Even though there was only a very low possibility of Kim Jong Nam becoming the leader of North Korea, China likely thought it would not hurt to protect him as long as that possibility existed."

(This article is based on reports by Koichi Furuya in Beijing, Yoshihiro Makino in Seoul, and Etsushi Tsuru and Masanobu Furuya in Kuala Lumpur.)