North Korean soldiers have stepped up patrols in one area of the Demilitarized Zone separating the two Koreas, but the move was not seen as alarming, the U.S. military said Wednesday.

The increased patrols coincide with heightened international efforts to defuse North Korea's tense standoff with the United States over its nuclear weapons programs. The communist country announced last week it would pull out of the Nuclear Nonproliferation Treaty.

"Over the past week, we have some increased activity," said Lt. Col. Matthew Margotta, who commands a combined battalion of U.S. and South Korean soldiers stationed near the border village of Panmunjom.

He described the activity as "not alarming, just unusual."

The 2.5-mile-wide, 156-mile-long DMZ has been the site of numerous infiltrations and violent confrontations over the decades, though such incidents have diminished in recent years.

Margotta said the North Koreans had increased patrols in the Joint Security Area, which encompasses Panmunjom. He said they had also occupied a guard tower on the northern side that hadn't been used in years.

"It's usually triggered by a heightening of tensions," Margotta said of the activity. He added that North Koreans took similar steps around the time of a June 29 naval clash between South and North Korean ships off the west coast of the peninsula.

Margotta said the U.S.-led U.N. Command, which oversees the southern half of the Demilitarized Zone, had not increased its own activity, and that U.S. military officials had not noticed any increased activity outside the Joint Security Area.