North Korea is equipping its border patrol boats with U.S.-made Gatling guns, the Yonhap News Agency reported Tuesday.

Yonhap quoted unnamed military sources, who told the agency that North Korea has been replacing its aging weapons systems with the rotary gun.

"If all the 380-something North Korean littoral combat boats are armed with the machine gun, this would pose an added threat to our Navy," the military source was quoted as saying by Yonhap.

South Korean and U.S. military officials are tracking down how the guns ended up in the hands of the North Koreans, Yonhap quoted sources as saying.

Many North Korean boats used hand-operated 30-millimeter cannons.

Yonhap quoted the sources as saying the weapon replacement appears to be aimed at strengthening the country's close-quarter combat capabilities.

Another military source said North Korea is moving to use stealth technology on its littoral combat ships in response to South Korea's move toward fast, stealthy patrol ships, Yonhap reported.