Vietnam's foreign ministry urged China to release nine of its citizens who were arrested on September 11 while fishing near the Hoang Sa Archipelago (Paracel Islands).
The ministry's representative made the demand on Tuesday at a meeting with the Chinese Embassy.
The Chinese responded by saying that the fishermen had used explosives for fishing, so Chinese agencies fined them and would release them upon receiving payment for the fines from their families.
In an interview with Thanh Nien, Bui Phu Phu, Deputy Chief of the Quang Ngai Coast Guards' headquarters, said China asked for 70,000 yuan (US$10,461) in fines.
However, the Vietnamese ministry said the fishermen from the central province of Quang Ngai were arrested while fishing in Vietnamese waters with nets and lights.
In an announcement sent to the Vietnamese Embassy in China, Chinese agencies didn't mention that the fishermen had used explosives, according to the ministry.
China has critically violated Vietnam's sovereignty and sovereignty right, the ministry said, demanding the northern neighbor unconditionally free the fishermen at once.
Since the fishermen were taken into custody, the Vietnamese ministry has met with Chinese officials in Hanoi and Beijing many times.
On September 21, the ministry sent a written demand on the release to the Chinese Embassy.
According to the Quang Ngai People's Committee, 22 fishing boats with 98 fishermen are currently being held in custody by foreign powers.