Maritime disputes involving China, Vietnam and the Philippines have flared up, escalating the risk of armed clashes in the resource-rich South China Sea.
Chinese and Vietnamese vessels were involved in a collision near the Paracel islands following the placement of a Chinese oil rig in waters claimed by both sides.
Vietnam yesterday accused Chinese vessels of deliberately ramming into Vietnamese patrol ships and also of using water cannon on its ships, causing damage and injuries in more than one incident since China announced last Saturday that the rig was operating in the area.
A Chinese plane also tried to intimidate the Vietnamese ships, a maritime official said.
Despite the heightened tensions, a Vietnamese official was quoted by Reuters as saying that no shots had been fired yet.
"Vietnam won't fire unless China fires first," he added.
Singapore yesterday urged all parties to exercise self-restraint and manage disputes peacefully according to international law.
"We also continue to urge Asean and China to work towards an early conclusion of the Code of Conduct in the South China Sea," the Ministry of Foreign Affairs said in a statement.
Separately, Chinese Foreign Ministry spokesman Hua Chunying yesterday demanded that Manila release 11 Chinese fishermen and their boat detained near the Spratly islands on Tuesday.
China also warns the Philippines not to make any more provocative moves, Ms Hua said.
She said the fishing boat and its 11-man crew were detained at the Half Moon Shoal near the Spratlys, which the Chinese call Nansha.
The Philippine police confirmed that it had "apprehended" a Chinese fishing boat and its crew, along with 350 turtles, some of which had already died.
A maritime police official said a Philippine boat, its crew and 70 turtles had also been seized.
The boats were towed to Palawan island, located about 100km from the shoal. The fishermen would face "appropriate charges", he added.
Several species of sea turtles are protected under Philippine law.
Analysts say the latest disputes could increase the risk of armed confrontations. Apart from Vietnam, the Philippines and China, which claims over 90 per cent of the South China Sea, Malaysia, Brunei and Taiwan are also claimants.
Singapore-based analyst Ian Storey said Vietnam looked increasingly prepared to use its navy, air force and maritime agencies "to confront the oil rig, prevent it from starting drilling operations, and ultimately to force China to withdraw it".
"This raises the very real prospect of a military clash between Vietnamese and Chinese forces, accidental or otherwise, which could then rapidly develop into a major crisis," he added.
Analysts say China's move could have been prompted by United States President Barack Obama's recent Asian tour that saw Washington and Manila inking a new defence cooperation pact.
Dr Storey, of the Institute of Southeast Asian Studies, said China's action could also have been prompted by reports late last year that PetroVietnam and ExxonMobil had begun developing a large natural gas field near where the Chinese oil rig is operating. "Beijing is sending a clear message to Hanoi: Stop plundering resources that rightfully belong to China," he said.
It was a point made by Chinese State Councillor Yang Jiechi on Tuesday. In a telephone conversation with Vietnamese Deputy Prime Minister Pham Binh Minh, he said no country has the right to interfere with Chinese companies' operations in waters that are "China's inherent territories".
Mr Minh told Mr Yang that Vietnam wanted China to remove the rig and hold talks to resolve the issue.