The spokesperson for the State Department Matthew Miller speaks during a press briefing in Washington, June 6. Yonhap

A U.S. State Department spokesperson called on North Korea Thursday to stop provocative activities as tensions have flared anew due to the North's recent sending of trash-filled balloons to the South and its troops' brief incursion across the inter-Korean border.

Matthew Miller, the spokesperson, made the call, reiterating America's security commitment to South Korea.

"We continue to call on North Korea to halt these activities," he told a press briefing. "We just reaffirm that our commitment to our South Korean allies is ironclad."

On Sunday, some 20 North Korean soldiers crossed the Military Demarcation Line inside the Demilitarized Zone (DMZ) separating the two Koreas, but retreated back to the North after the South Korean military fired warning shots, according to Seoul officials.

The incursion came just hours before the South conducted anti-Pyongyang broadcasts near the border for the first time in six years in response to the North's recent launches of waste-loaded balloons.

Last week, Miller condemned the North's balloon operation as a "disgusting" and "childish" move. (Yonhap)