The State Department said Wednesday North Korea's alleged execution of a top military official, if confirmed, would show "another extremely brutal act" by the communist regime.

South Korea's main intelligence agency, the National Intelligence Service, reported to lawmakers earlier Wednesday that the North executed its defense chief, Hyon Yong-chol, late last month with an anti-aircraft gun for showing disloyalty to leader Kim Jong-un.

"We've seen the press reports about the execution of North Korean officials. I'm not in a position to confirm any of those specifics. But these disturbing reports, if they are true, describe another extremely brutal act by the North Korean regime," said the State Department's acting deputy spokesperson, Jeff Rathke.

"And these reports, sadly, are not the first in this regard," he said.

Hyun, 66, was punished for dozing off when leader Kim was delivering a speech at a military event last month, talking back to the leader, failing to carry out his instructions, and expressing complaints about him, according to the NIS.

North Korea has often carried out public executions in what critics say is aimed at instituting a reign of terror to consolidate Kim's grip on power that he inherited upon the death of his father and long-time leader, Kim Jong-il, in 2011.

In 2013, Kim ordered the execution of his once-powerful uncle, Jang Song-thaek, who was accused of treason, a shocking purge that drew widespread condemnation and sparked concerns over possible instability.

Since taking power, Kim has had about 70 senior officials executed, according to the NIS. (Yonhap)