Le Lon, who along with 20 other Vietnamese nationals was released Friday after 49 days in Chinese custody, said he had been mistreated by his jailers and kept in harsh conditions. "We were each given just two bowls of rice with some vegetables and very little water every day," Lon, 46, said.

"All of us were kept in a room of around 40 square metres. We slept on the cement floor without mats," he said by phone from Ly Son island. The two Vietnamese fishing boats and crew were picked up by China early March for fishing near the Paracel Islands - known as Hoang Sa in Vietnamese and Xisha in Chinese - which are claimed by both countries.

One of the two Vietnamese vessels brought the fishermen back home but one is still being held by China, Lon said, adding he and the captain of the other Vietnamese boat had been repeatedly questioned by Chinese authorities.

The incident was the latest in a string of diplomatic rows in the South China Sea involving Beijing and a host of other regional nations.

China says it has sovereign rights to all the disputed waters, believed to sit atop vast oil and gas deposits, including areas close to the coastlines of other countries and hundreds of kilometres from its own landmass.

China and South Vietnam once administered different parts of the Paracels but after a brief conflict in 1974 Beijing took control of the entire group of islands - although this remains disputed by Hanoi.

The islands are a constant source of tension between the two neighbours, exacerbated by additional disputes over the Spratly archipelago -- also in the South China Sea. Earlier this month, a Chinese cruise operator said one of its ships had gone on a trial tour to the Paracel islands, in another move that angered Hanoi, which said the trip was "illegal."

Agence France Presse - April 23, 2012