U.S. Secretary of Defense Chuck Hagel and Gen. Martin Dempsey, who oversees field operations of American troops, voiced strong concerns Thursday about increased uncertainties surrounding North Korea and the possibility of additional provocations.

Hagel stressed that North Korea's execution of Jang Song-thaek, a putative number two official, demonstrates the unpredictability of the communist regime.

It is "very concerning to everyone and reality of that uncertainty heightens the tensions," Hagel said at a news conference at the Pentagon.

U.S. officials have long stated that it is difficult to gain credible information about a nuclear-armed North Korea.

The sudden removal of Jang, an uncle of young leader Kim Jong-un and reportedly one-time regent for him, complicates the international community's efforts to fathom the secretive nation's intentions.

"It further deepens the suspicions of motives," Hagel added.

"That nation is as closed as any nation in the world. There is no transparency."

Sitting next to him, Dempsey, chairman of the joint chiefs of staff, said the North's recent move apparently heralds another provocative step.

"These kind of internal actions by dictators are often a precursor to provocation to distract attention from what they are doing inside of that country," he said.

In Seoul, South Korean Defense Minister Kim Kwan-jin also said earlier that chances are high the North will take provocative actions early next year or in spring, when the country will have some big national events and Seoul-Washington joint military drills are planned on the peninsula.

Meanwhile, Hagel put the blame on China for a dangerous incident in early December which elevated naval tensions with the U.S.

A Chinese warship nearly collided with U.S. Navy guided missile cruiser USS Cowpens, which was in international wasters in the South China Sea.

"That action by the Chinese, cutting in front of their ship, 100 yards out in front of the Cowpens, was not a responsible action," the secretary said. "That's the kind of thing that's very incendiary, that could be a trigger or a spark that could set off some eventual miscalculation." (Yonhap News)