The Wall Street Journal says a North Korean arms chief and Pyongyang’s former ambassador to the United Nation’s nuclear energy agency have emerged as key figures in an intensifying international effort to curb North Korea's weapons-trading activities.

The daily said Yun Ho-jin, the head of the Namchongang Trading Corporation, and Chun Byung-ho, who heads the North’s Second Economic Committee, have played leading roles in North Korea's development, proliferation and testing of atomic weapons.

Both the Second Economic Committee and Yun, who is believed to have procured aluminum tubes from a German businessman for uranium enrichment efforts around 2003, were included Tuesday in a new list of entities and individuals that would face U.S. sanctions.

According to current and former U.S. officials, Chun and Yun allegedly have played important roles in strengthening Pyongyang's military ties to countries such as Syria and Myanmar.

The paper said Yun is believed to be the husband of Chun’s second daughter.