Vietnamese naval ships and Chinese vessels have collided in the South China Sea, Vietnamese officials say.

The incident happened as the Vietnamese navy was trying to prevent the Chinese from setting up an oil rig in an area claimed by both nations.

No shots were fired, reports say. But Vietnamese officials said that water cannons were used on their ships.

The incident is the most serious between the countries at sea in years, with dozens of boats now in the area.

Vietnamese officials said on Wednesday that the Chinese ships intentionally rammed their vessels.

Several sailors were injured, AP quoted one official as saying.

Vietnamese maritime police official Ngo Ngoc Thu told media in Hanoi on Wednesday that Chinese boats had collided with Vietnamese vessels three times since 3 May.

Read more: http://www.bbc.com/news/world-asia-27293314