A North Korean nuclear envoy was tight-lipped on Wednesday when asked about the North's test launch of two intermediate-range ballistic missiles earlier in the day.

South Korean defense officials said North Korea test-fired two mid-range ballistic missiles into the East Sea in the North's latest violation of U.N. Security Council resolutions that ban Pyongyang from using ballistic missile technology.

The Wednesday tests come as North Korea sent its nuclear envoy, Choe Son-hui, deputy director for North American affairs at North Korea's foreign ministry, to Beijing to attend a security forum that also brings together nuclear envoys from nations involved in long-stalled nuclear negotiations with the North.

Choe was entering the closed-door forum when she was asked by reporters about the North's missile tests. But she did not respond to the questions.

Among those attending the Northeast Asia Cooperation Dialogue, which began its two-day run on Wednesday, are Ambassador Sung Kim, a top U.S. envoy on North Korea policy; Kim Gunn, South Korea's deputy chief nuclear envoy; and Wu Dawei, China's chief nuclear envoy.

On Tuesday in Beijing, the U.S. envoy warned North Korea against launching a mid-range ballistic missile.

"North Korea should not be engaged in any activities in violation of clear U.N. Security Council obligations and commitments," Kim told reporters at the Beijing airport. 

The nuclear envoys from the U.S. and South Korea have ruled out holding a bilateral meeting with Choe on the sidelines of the forum.

North Korea, which conducted its fourth nuclear test in January this year, did not attend the NEACD in 2014 and 2015.

The six-party talks were last held in late 2008. Diplomatic efforts to resume the negotiations on ending North Korea's nuclear ambitions have produced few results, as the North has shown no signs of giving up its nuclear weapons program.  (Yonhap)