GUANGZHOU - Chinese authorities on Friday released 21 Vietnamese fishermen and their two fishing boats, who had been detained for over a month at China's Xisha Islands over allegations of illegal fishing.

The fishermen were released after they guaranteed in writing not to infringe on China's maritime rights, especially fishing, in its territorial waters, the South China Sea Fishery Bureau under the Ministry of Agriculture announced.

China's patrol ship detained the Vietnamese fishermen at Xisha Islands on March 4. The Vietnamese fishing boats were loaded with 25 kilograms of explosives, other tools for dynamite fishing, and hundreds of kilograms of sea catches when they were caught.