A large number of North Korean propaganda leaflets were found at a local university Tuesday as the isolationist country steps up its campaign to highlight its nuclear achievements and sow internal discontent within South Korea.

Police retrieved some 1,500 leaflets from Seoul National University's Gwanak campus in southern Seoul.

The leaflets carried criticism of President Park Geun-hye. They also urged young adults not to enter the military. Law enforcement officials did not elaborate on how the leaflets reached the school.

In South Korea, all able-bodied men are required to serve about two years of mandatory military service, as the country is technically still at war with North Korea after the 1950-53 Korean War ended in an armistice agreement, not a peace treaty.

On Monday, another 1,500 leaflets were found along the mountain side near the school, according to police.

They said the North probably sent the leaflets in an apparent response to the joint military exercises between South Korean and the United States.

Last week, the allies kicked off their largest-ever annual military exercises, amid escalating military tensions between South and North Korea following Pyongyang's nuclear and long-range missile tests earlier this year. (Yonhap)