Anti-China protesters Sunday rallied in Vietnam over disputed islands but were kept away by police from Bejing's diplomatic missions after a protest last week sparked a rebuke from China.
Several hundred demonstrators in Hanoi and Ho Chi Minh City marched in the long-simmering dispute over the Spratly and Paracel archipelagos in the South China Sea, which are claimed by China, Vietnam and other regional countries.
Police prevented about 300 demonstrators in the capital and around 100 in the southern port city formerly called Saigon from protesting outside the embassy and consulate of Vietnam's northern neighbour and communist ally.
Similar noisy but peaceful rallies on December 9, which supported Vietnam's official territorial claims, were tolerated by police for about one hour, triggering a diplomatic protest from Beijing two days later.
"We are highly concerned over the matter," said China's foreign ministry after the first protest.
"We hope the Vietnamese government will take a responsible attitude and effective measures to stop this and prevent bilateral ties from being hurt."
In the latest rally, groups of demonstrators marched through Hanoi, waving flags, shouting anti-China slogans and singing patriotic songs.
Most of the protesters wore identical T-shirts with the red-and-gold Vietnamese flag, a map of Vietnam that included the islands, and the words "China hegemony jeopardises Asia" and "Beware of the invasion."
In Ho Chi Minh City around 100 demonstrators were rallying at a park near the Chinese consulate, holding up signs that read "Hands off Vietnam," "Vietnam: United We Stand" and "Stop Chinese Expansion."
The two archipelagos -- called Truong Sa (Spratlys) and Hoang Sa (Paracels) in Vietnamese --- are considered strategic outposts in the South China Sea, have potential oil and gas reserves and rich fishing grounds.
The Spratlys, more than 100 islets, reefs and atolls, are claimed in full or part by China, Vietnam, the Philippines, Malaysia, Brunei and Taiwan.
The Paracels -- which Chinese troops took from South Vietnamese forces in 1974 -- are also claimed by Vietnam and Taiwan.
The disputes stir strong passions in Vietnam, which remembers a millennium of Chinese rule and fought its last border war with China in 1979. A naval clash in 1998 near one of the Spratlys killed more than 50 Vietnamese sailors. The street protests started on December 9 after China set up a county-level government unit which covers 2.6 million square kilometres (1 million square miles), mostly ocean, including the disputed isles.
The issue has been hotly debated on blogs in Vietnam, and Vietnamese hackers have defaced at least one Chinese government website.
The islands have been flashpoints for years, and the number of disputes has risen as declining fish stocks have forced fishing crews from Vietnam and elsewhere to sail deeper into disputed waters.
In July a Chinese naval vessel fired at a Vietnamese fishing boat near the Spratlys, sinking the boat and killing one sailor, reports said.
Vietnam expert Carl Thayer said China was pursuing "a policy of creeping assertiveness" in the region, which conflicts with Vietnam's maritime strategy of maximising the development of its offshore resources by 2020.
"Chinese naval vessels have reportedly fired on Vietnamese fishing boats," said Thayer, of the Australian Defence Force Academy.
Beijing had also pressured oil company British Petroleum to stop developing an area off southern Vietnam, he said.
"China has the upper hand because it can threaten the interests of foreign companies who operate in both China and Vietnam," he told AFP.
Thayer, a veteran Vietnam watcher, said public rallies in Vietnam critical of China are "unprecedented and may represent the first step in a prolonged information campaign to win over international sympathy and support."