This picture taken on March 5, 2018 and released from North Korea's official KCNA on March 6, 2018 shows North Korean leader Kim Jong-Un (C) meeting with the South Korean delegation in Pyongyang.

The United States has decided Pyongyang used the chemical warfare agent VX to assassinate the half-brother of North Korean leader Kim Jong Un in Malaysia in 2017 and has imposed additional sanctions on the country, the U.S. State Department said on Tuesday.

State Department spokeswoman Heather Nauert said in a statement the U.S. government made the determination on Feb. 22 under the Chemical and Biological Weapons Control and Warfare Elimination Act of 1991. Additional sanctions on Pyongyang went into effect on March 5 after the finding was formally published, she said.

Kim's estranged half-brother, Kim Jong Nam, was killed at the airport in Kuala Lumpur when two women smeared his face with the banned chemical weapons agent VX.