Hundreds of leaflets praising North Korea were found in Seoul Saturday, police said, as the communist country held a major political event in defense of its monolithic regime.

The leaflets, which were discovered by a passerby in the western Yangcheon Ward earlier in the day, contained text that hailed North Korea's nuclear weapons development and criticized South Korean President Park Geun-hye, according to the police.

Police said they immediately gathered the leaflets, of which there were about 300 to 400, and handed them over to the military as they appeared to have been sent from the North.

Speculation arose that Pyongyang may have sent the leaflets as part of anti-South Korea psychological warfare in time for the 7th congress of its ruling Workers' Party, which opened on Friday.

The congress, which is being held for the first time in 36 years, is attracting close scrutiny by the outside world for any developments in the North's policies after the country was slapped with toughened international sanctions over its nuclear and missile tests earlier this year.

Propaganda leaflets are a sensitive issue between the Koreas.

In October 2014, the two sides exchanged machine gun fire across the border after the North apparently tried to shoot down balloons carrying anti-Pyongyang leaflets.

The Koreas remain technically at war as the 1950-53 Korean War ended in an armistice, not a peace treaty. (Yonhap)