HANOI (AP) ― A Chinese fishing vessel rammed and sank a Vietnamese fishing boat in the disputed South China Sea, Vietnamese state media reported Tuesday, an incident likely to sharpen already dangerously high tensions between the two nations over their overlapping claims in the waters.

The reports in the Tuoi Tre newspaper and other media said the incident occurred around 30 kilometers from a large oil rig China deployed May 1 in a section of the sea claimed by both countries. The move by Beijing infuriated Hanoi and set off violent anti-China protests.

Vietnam sent patrol ships to confront the rig, and China has deployed scores of vessels to protect it.

The two sides have been involved in a tense standoff, occasionally colliding with each other.

The countries have long sparred over who owns what in the oil and gas-rich waters. Incidents between fishing crews are quite common.

Tuoi Tre said about 40 Chinese fishing boats surrounded a group of Vietnamese ones on Monday afternoon.

It said one them rammed into the Vietnamese, tossing 10 fishermen into the water and sinking the boat. The fishermen were picked by the other Vietnamese boats and there were no injuries.

It was impossible to independently verify that account of the incident.

Since May 1, Vietnam has accused China of ramming into or firing water cannons at Vietnamese vessels trying to get close to the rig, damaging several boats and injuring fisheries surveillance officers. They have shown video footage of some of the incidents. China accuses Vietnam of doing the same.

China claims nearly all of the South China Sea as its own, bringing it into conflict with the far smaller nations of Vietnam, the Philippines and three others that have rival claims. In recent years it has been more assertive in pressing its claims in the waters and resisting attempts to negotiate.

The United States, which shares the concerns of the smaller claimant states about China’s rising military might, called China’s deployment of the rig “provocative.” Vietnam is trying to rally regional and international support against Beijing, but its options are limited because China is the country’s largest trading partner.