Hundreds of Vietnamese demonstrated in Hanoi on Sunday against China's moves to strengthen its claim to disputed islands in the South China Sea and its invitation to oil firms to bid for blocks in offshore areas that Vietnam claims as its territory.
The authorities in Vietnam rarely allow public demonstrations and some bloggers said security forces had warned them against attending the rally, but the police made no attempt to disperse people, Nguyen Quang A, one of the protesters said.
"We want to raise people's awareness of China's wrongful moves recently, and we have received applause from people in the streets," he said.
The authorities tolerated a series of protests over China's territorial claims from June to August last year before the government put an end to them.
CNOOC, the parent of New York- and Hong Kong-listed CNOOC Ltd, issued a tender last Saturday to invite foreign companies to jointly develop nine blocks in the western part of the South China Sea.
Vietnam has called this move illegal because the blocks encroach on what it claims are its territorial waters.
"The area that the China National Offshore Oil Corporation announced to open for international bidding lies entirely within Vietnam's 200 nautical mile exclusive economic zone and continental shelf in accordance with the 1982 United Nations Convention on the Law of the Sea," Vietnamese Foreign Ministry spokesman Luong Thanh Nghi said on June 26.
"It is absolutely not a disputed area," he said.
Vietnam state oil and gas group Petrovietnam has said one of the nine blocks offered for bidding by CNOOC is just 37 nautical miles (69 km) from the southern province of Binh Thuan's Phu Quy island.
It said it has been exploring for oil and gas with Exxon Mobil Corp of the United States, Russia's Gazprom and India's ONGC Videsh in most of the blocks offered by CNOOC.
Hanoi has also denounced a move by China to change the administrative status of Sansha City as a way of enforcing its claims to several largely uninhabited islands, including the Paracels and Spratlys.