SEOUL - A North Korean ship was seen sailing in international waters off South Korea's west coast Sunday after being tracked by the US Navy on suspicion of carrying weapons, a report said.

The South Korean military was on watch as the Kang Nam 1 headed back to its home port in the Yellow Sea, Yonhap news agency said. South Korean officials declined to comment.

Yonhap quoted an unnamed government official as saying the ship is expected to reach North Korean waters Monday morning.

The vessel, which left home on June 17, was originally reported to be bound for Myanmar but it changed course after being followed by the US Navy on suspicion of carrying weapons.

It was the first North Korean ship to be tracked under new UN sanctions imposed on the hardline communist country following its nuclear test in May.

Under the measures UN member states are expected to inspect ships they believe may be carrying banned weapons shipments to or from the North.

Pyongyang has responded defiantly to the UN move, vowing to build more nuclear bombs and to hit back against any attempt to search its vessels.

South Korea's chief nuclear negotiator Wi Sung-lac and his Japanese counterpart, Akitaka Saiki, will meet in Seoul Monday for talks on how to implement UN sanctions, Yonhap said.

China's chief nuclear envoy, Wu Dawei, is scheduled to visit Seoul on July 12-14.