HANOI, Vietnam (AP) — A Vietnamese government official says Vietnamese navy and coast guard vessels are trying to prevent a Chinese oil rig from establishing a fixed position in a disputed part of the South China Sea and that vessels from the two countries have collided.

The official said no ammunition had been fired and there were no reports for injuries.

The standoff Wednesday close to the Paracel Islands raises the possibility of skirmishes in one of Asia’s most volatile regions.

Earlier two foreign diplomats said Vietnam dispatched up to 29 ships to the area near the oil rig when it became aware of China’s intentions on May 2.

All spoke on condition of anonymity because of the sensitivity of the information.