Phan Huy Hoang, an official in central Quang Ngai province where the fishermen came from, said a Chinese vessel slammed into the fishing boat with 10 fishermen on board near the Paracels islands on Sept. 29 and sank it. The fishermen were rescued by another Vietnamese fishing boat and the case was reported to authorities when the fishermen returned home two days ago.

"Chinese actions against fishermen from Quang Ngai province have been more aggressive and brutal," Hoang said by telephone from Quang Ngai.

More than 20 Vietnamese fishing boats have been attacked by Chinese vessels this year including the sinking of a fishing trawler in July, he said, adding a formal protest will be made to China.

Dang Dung, the captain of the boat, said he and nine crew members were sleeping after a night of fishing when the Chinese vessel slammed the side of their boat and then five Chinese men jumped onto their boat.

Dung said by telephone from Quang Ngai that the men were armed with knives and took away the boat's navigation devices, fishing equipment and their catch.

He said his leaking boat sank about 12 hours later, and the crew then spent four hours floating with life vests in the water before being rescued by another Vietnamese fishing boat.

Vietnam and China both claim the Paracels islands, which were occupied by China after ousting the U.S.-backed South Vietnamese navy in 1974, one year before the end of the Vietnam War.

The two countries along with the Philippines, Malaysia, Brunei and Taiwan also claim parts or all the Spratlys islands in the South China Sea, an area which occupies a busy international sea lane and is rich in oil and gas and fish resources.

The Associated Press - October 15, 2015