North Korean leader Kim Jong Un greets a women's subunit during a rocket launching drill Reuters/KCNA KCNA SEOUL (Reuters) - North Korea on Monday resumed a campaign of loudspeakers blasting propaganda across its border with South Korea, days after the South took a similar step in response to a landmine explosion in the Demilitarised Zone (DMZ).

Tension between Pyongyang and Seoul is rising as U.S. and South Korean forces on Monday began annual joint military exercises that the North regularly protests.

On Aug. 4, two South Korean soldiers were wounded by a landmine in the heavily-fortified demilitarized zone, which Seoul said was planted by the North. The North denies involvement.

A week later, the South began using loudspeakers to broadcast anti-Pyongyang rhetoric across the western and central parts of the border, resorting to a practice suspended by both sides since 2004.

"We understand that the North Korean military has resumed anti-South Korean propaganda broadcasts via loudspeakers at some eastern parts of our border," a South Korean defense ministry official said.

South Korea plans to expand its own broadcasts, the official said, without giving details, citing the secretive nature of psychological warfare.

On Saturday, North Korea demanded that the South halt the broadcasts, or face military action for what it called a "declaration of war".

The DMZ is a 4-km- (2.5-mile-) wide buffer fortified with landmines and barbed wire stretching across the Korean peninsula. It has divided the two Koreas since the end of the 1950-53 Korean War.

(Reporting by Ju-min Park and Sohee Kim; Writing by James Pearson; Editing by Tony Munroe and Clarence Fernandez)