SEOUL, South Korea (AP) _ North Korea says South Korea mistook ``normal blasting'' from a construction project for artillery shelling when it accused Pyongyang of opening fire near the rivals' disputed maritime line in the Yellow Sea.

North Korea said Thursday the South was simply frightened by noise from nearby building efforts ``aimed at improving the standard of people's living.''

South Korean defense officials say marines returned fire Wednesday after North Korea launched artillery shells into waters near the disputed Northern Limit Line that separates the countries.

The North says in a statement released by the official Korean Central News Agency that it's ``preposterous in the age of science when latest detecting and intelligence means are available that they mistook the blasting for shelling.''