North Korea has strengthened its border controls to try to stem the steady stream of defections to South Korea, Seoul\'s Yonhap News Agency reported Friday. The latest crackdown came after nine North Koreans crossed the tense western sea border into South Korea aboard two engineless boats in June, the Good Friends said in its newsletter, according to the report. The North bans small motorless boats on its western coast and thoroughly vets people before issuing permits to go to sea. It also stopped issuing a travel permit that made it nearly impossible for inlanders to travel to border areas - crossing points for defectors, the aid group said. However, the flow of North Korean defectors continues amid chronic food shortages and harsh political oppression. South Korea is now home to more than 21,000 North Korean defectors and defections are a constant irritant to inter-Korean relations. South Korea has suggested that it will not return the nine North Korean defectors to the North despite Pyongyang warning of further damage to inter-Korean relations. Seoul has a longstanding policy to accept any North Korean defectors who want to live in the South, and repatriate any North Koreans who stray into the South if they want to return. The two Koreas are still technically at war as the 1950-53 Korean War ended in a truce, not a peace treaty. ad