South Korea
South Korean Marines take part in a U.S.-South Korea joint landing operation drill in Pohang, South Korea, March 12, 2016. REUTERS/Kim Hong-Ji

The South Korean military is on high readiness after North Korean leader Kim Jong Un’s brother Kim Jong Nam was killed in Malaysia allegedly by two women earlier this week, Seoul’s Joint Chiefs of Staff (JCS) said Thursday.

Although South Korea has not detected any provoking move from the North, its military said it fortified its surveillance and defense capabilities to counter any possible attack from its rival neighbor, South Korea's Yonhap News Agency reported, citing a JCS official.

"If the cause of the half brother's death is officially announced by (the Malaysian government), we may consider delivering the news through loudspeakers to North Korean soldiers and citizens near the border," the official said.

Kim Jong Nam, the North Korean leader’s step brother and the eldest son of the late North Korean leader Kim Jong Il, was believed to have been poisoned Monday when he was preparing to board a flight home to Macau from Kuala Lumpur International Airport. The killing triggered speculation that Kim Jong Un sent agents to murder his brother.

So far, Malaysian authorities have taken two women and a man into custody. Local law enforcement authorities said they were working to determine the identities of the suspect. It remains unclear whether the women killed Kim Jong Nam.

An autopsy on Kim Jong Nam was completed but the results have not been released. The findings would reveal whether he was poisoned.

North Korea wanted to kill Kim Jong Nam for several years, according to Lee Byung-ho, the director of South Korea's National Intelligence Service. However, the plan was not executed as he was reportedly being protected by China.

At the time of his death, Kim Jong Nam was traveling with a passport with the name Kim Chol. He is reported to have been considered Kim Jong Il's favorite son before his brother took power in 2011.