State media gave no details of specific incidents.

"Vietnam's indisputable sovereignty over the Truong Sa (Spratly) and Hoang Sa (Paracels) archipelagos is confirmed by historical evidence and has a legal basis," Dung added.

Vietnam, Brunei, Malaysia, the Philippines as well as China and Taiwan all claim the Spratly Islands, a potentially oil-rich chain of islands.

The 10-member Association of Southeast Asian Nations (ASEAN) signed a treaty with China in November last year hoping to prevent an escalation of tensions over the Spratlys.

All parties agreed to refrain from activities that would escalate tensions in the region. The deal involved the four Southeast Asian nations and China, but excludes Taiwan.

Vietnam and China have clashed twice over the Spratlys, in 1988 and 1992, while skirmishes have also occurred between other countries, testing relations while threatening to undermine regional security.

"While accelerating the negotiations for essential and long-term solutions to disputes, related parties should maintain stability, preserve the status quo, show self-restraint and refrain from aggravating the situation," Dung said.

Although it is believed the archipelago sits on top of vast reserves of oil and gas, their commercial potential has never been confirmed. The islands also flank international shipping lanes.

Vietnam said last month it was mulling tourist trips to Spratlys.

- AFP