Kim Jong-nam, the half-brother of North Korean authoritarian leader Kim Jong-un, was reportedly assassinated in Malaysia on Monday, South Korea’s Yonhap News reported. Officials said two unidentified women attacked him with “poisoned needles” before fleeing the site, TV Chosun reported.

The incident triggered speculation that North Korean agents may be responsible for the murder.

Kim Jong-nam, the eldest son of late dictator Kim Jong-il, had challenged his half brother’s succession to the top post. Officials said he had been trying to takeover the reigns of the isolated nation. Jon-nam was living abroad after a reported dispute with his father over his attempt to enter Japan with a fake passport.

He was born from the former leader’s extra-marital relationship with South Korean actress Sung Hae-rim, Yonhap News reported. The South Korean government is yet to respond to the reports.