Vietnam's coast guard has seized a Chinese oil tanker which it claims intruded into Vietnamese waters, state media said Monday, the latest episode in a festering territorial dispute in the South China Sea.

The Qiong Yangpu was carrying 100,000 litres of oil, the official Vietnam News Agency said, adding that it was captured Thursday and impounded in the northern port of Hai Phong.

The three-man crew was handed over to police, the report said.

"It was spotted and seized by Hai Phong coast guards... 12 nautical miles from the marine delineation line in the Tonkin Gulf to the northwest of Vietnam's Bach Long Vi island," the report said.

Police, military, and coast guard officials in Hai Phong declined comment Monday.

According to the state-run Tuoi Tre newspaper, the tanker was selling oil to Chinese fishing boats in the area.

"The captain, however, failed to present relevant documents to prove the origin of the oil, while his two crew members have no operating licence," Tuoi Tre said.

Vietnam and neighbouring China have longstanding territorial disputes over the Spratly and Paracel Islands, and often trade diplomatic barbs over oil exploration and fishing rights in the South China Sea.

Vietnam regularly chases Chinese fishing vessels out of waters it claims, but it is rare for authorities to hold a boat and its crew.

In recent years China has begun aggressively patrolling near the contested islands and Vietnamese officials accuse it of imposing fishing bans and using patrol boats to keep foreign trawlers out.

Hanoi says hundreds of its fishing boat crews have been arrested by Chinese authorities over the last few years.

Beijing has occupied the Paracels, known as Xisha in Chinese, since a brief war with South Vietnam in 1974.

It also claims the Spratlys, as do -- in whole or in part -- Taiwan, Malaysia, the Philippines and Brunei as well as Vietnam.

Beijing claims as its historical territory virtually all of the South China Sea, which is believed to sit atop huge oil and gas reserves.