Vietnam's coast guard has seized a Chinese vessel for intruding into its territorial waters, say local media.
The ship, carrying more than 100,000 litres of fuel, was stopped near the northern maritime border last week.
Vietnamese media say the crew admitted they were supplying fuel to Chinese fishing boats in the area.
The government-owned Vietnam News Agency said the seized vessel had been disguised as a fishing boat.
The report comes amid accusations from Malaysia and Indonesia that Chinese fishing vessels, backed by the Chinese coast guard, are intruding into what the countries consider as their sovereign waters.
There has been no comment from China.
This incident makes the country the latest among South East Asian nations to be ensnared with disputes in the South China Sea over Chinese vessels entering territorial waters.
According to The Thanh Nien newspaper, that the vessel was towed to the northern port city of Hai Phong, and that the ship, its captain and two sailors, all Chinese, are under the supervision of Vietnamese authorities.