North Korean leader Kim Jong-un's estranged half brother Kim Jong-nam has reportedly been killed in Malaysia. 

A South Korean government official said the 46-year-old Kim was killed in the Southeast Asian country on Monday morning. 

Kim Jong-nam, the eldest son of the North's late former leader Kim Jong-il, has been living outside the country since his younger brother rose to power in 2012. Kim was born by Sung Hye-rim, the first wife of the former North Korean leader. 

An official at the presidential office Cheong Wa Dae said on Tuesday that it received reports from the ministries of defense and foreign affairs that Kim Jong-nam was killed at the Kuala Lumpur International Airport.

The Cheong Wa Dae official said that the ministries are checking the reported killing, but added that the top office has no plan to convene a session of the National Security Council at the moment. 

Kim Jong-nam had been groomed as the North's future leader just as his late father had inherited power from the North's founding leader Kim Il-sung.  

He reportedly fell out of his father's favor after he and his son along with two other women were caught while trying to enter Japan with fake passports through Narita Airport in 2001. They were later deported. 

Since his uncle Jang Song-thaek was executed in 2013, he had been living in Singapore and other Southeast Asian countries. 

There is speculation that he may have been killed by assassins sent by Kim Jong-un in order to remove an obstacle for his personality cult, given that he had been very critical of the dynastic power succession in the North. 

However, Kim Jong-nam has restrained from making public comments about the North's internal political situation after his half-brother strengthened his hold on power. 

The Foreign Ministry in Seoul declined to confirm whether he was assassinated by Kim Jong-un. 

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