China Vietnam dispute: Fishing boat rammed at sea
6 June 2014 Last updated at 10:17 BST
Vietnam's state television (VTV) has broadcast a video in which a large Chinese ship can be seen chasing and later sinking a small Vietnamese fishing boat.
Vietnamese and Chinese ships have been in a stand-off for a month after a Chinese owned oil rig, called Haiyang 981, was moved into waters claimed by both countries.
The VTV report called the incident "unarguable evidence of the inhumane actions of China against Vietnamese fishermen".
The Chinese government maintained that its vessels were "only in a defensive mode".
Kasia Madera reports.