The United States owes China a reasonable explanation as to why US B-52 bombers entered Chinese airspace near the Nansha Islands on Dec 10.

China's Defense Ministry urged the US to stop such dangerous and provocative actions, which have become another source of tension between both countries along with the US government's announcement of a new arms sale to Taiwan last week.

The Pentagon said the military aircrafts had strayed off course due to bad weather and an investigation has been launched.