Vietnam state television has broadcast video showing a Chinese ship colliding with a small Vietnamese fishing boat which capsizes in its path not far from where China has parked an oil rig in disputed waters.
Vietnam and China have already traded accusations over who was to blame for the May 26 incident, as tensions fester between the two countries over the giant drilling platform in the South China Sea.
The video, shot from a nearby Vietnamese craft, shows a much larger Chinese vessel steaming after two Vietnamese fishing boats.
It bisects the two boats, then the Vietnamese ship closest to the camera suddenly tips on its side into the path of the larger vessel and overturns.
At the moment of impact, one man on the boat from where the footage was filmed yells in Vietnamese: "Oh! The boat's sinking."
Vietnamese fishing boats operating nearby rescued the 10 fishermen from the sunken vessel, the government and the coastguard have previously said.
"The latest images recorded by Vietnamese fishermen at the time when fishing ship DNa-90152 was sunk by a Chinese ship serve as irrefutable evidence of the inhumane actions of China against Vietnamese fishermen," the VTV report said.
Chinese Foreign Ministry spokesman Hong Lei said it was the Vietnamese ships that were being aggressive.
"In these seas. China's ships were in a defensive mode ... who was it who took the initiative for the clash? Who was it who created tension on the scene? This is very clear," Hong said.
Last week, Hanoi said some 40 Chinese fishing boats had surrounded the Vietnamese craft before one of them rammed it and it sank. China's official Xinhua news agency, citing a government source, had said the vessel capsized after "harassing and colliding with" a Chinese fishing boat.
Scores of Vietnamese and Chinese ships, including coastguard vessels, have continued to square off around the rig despite a series of collisions after the platform was towed to the area in early May. Until the May 26 incident, no ship had sunk.
The Haiyang Shiyou 981 rig is drilling between the Paracel islands occupied by China and the Vietnamese coast.