“They not only sank the fishing boat but tried to prevent other boats from rescuing the fishermen,” said Phan Van On, a spokesman for the Quang Ngai provincial search and rescue agency.
The five-member Vietnamese fishing crew was returning to shore on Saturday when it was intercepted by a pair of Chinese boats, Thanh Nien newspaper reported.
Another fisherman in the area reported seeing the Chinese boats lingering near the stricken vessel for hours as its crew hung on to the bow.
“This action is merciless and pitiless and should be condemned,” PhanVan On told dpa.
The incident was made public one day before an international tribunal was expected to deliver its verdict on a case concerning maritime disputes between China and the Philippines in the South China Sea.
China claims most of the South China Sea with overlapping claims by Vietnam, Taiwan, the Philippines, Malaysia and Brunei.