About 150 people wearing headbands and carrying large banners circled the busy streets around Hanoi's Hoan Kiem lake chanting "down with invasive China". They laid wreaths for 64 Vietnamese sailors who died in a 1988 clash with Chinese forces in the Spratly islands.

The protest was small, but significant given Vietnam's history of preventing or breaking up demonstrations. While anti-China sentiment is strong among the public, it is a sensitive issue for the ruling Communist Party.

Police made no attempt to stop the 90-minute protest, which was larger than those last year, including one on the eve of Chinese President Xi Jinping's visit to Hanoi in November.

The rally comes amid tension, brinkmanship and a torrent of megaphone diplomacy in response to anything from Chinese flights and deployment of a missile system to U.S. "freedom of navigation" patrols and Japanese defense agreements with the Philippines.

Vietnam's Foreign Ministry last month accused China of taking actions that threaten peace and "accelerate militarization".

Monday's demonstration was over a battle in the Johnson Reef in the Spratly islands. Accounts of it differ greatly and Vietnam does not commemorate the incident officially.

"That was the first step in China's plan to militarize the South China Sea," said activist Nguyen Van Phuong, 29, referring to the 1988 hostilities.

Though Vietnam opposes China's occupation of the Paracel Islands and parts of the Spratly archipelago, its responses to Beijing's activities in disputed areas are usually measured and often come days after those of other countries.

China is Vietnam's biggest trade partner and the communist parties that run both countries have historically been close, although some Vietnamese leaders have said trust has been impacted of late.

By Martin Petty - Reuters - March 14, 2016

Vietnam’s anti-China activists mark anniversary of ‘long forgotten’ Gac Ma Island battle that left 64 soldiers dead

Vietnam’s communist leadership’s handling of its delicate relationship with China is a frequent flashpoint for domestic criticism of Vietnam’s authoritarian government.

Activists chanted anti-China slogans in the Vietnamese capital on Monday to mark the anniversary of a 1988 battle in the Spratly Islands, a rare act of protest over an issue that has come to dog relations between Hanoi and Beijing.

The two neighbours are locked in long-standing territorial disputes over the Spratly and Paracel Islands, which both countries claim.

One-party Vietnam clamps down on public protest. But anti-Chinese demonstrations have become increasingly commonplace, particularly around the March 14 anniversary of a skirmish between China and Vietnam.

In 1988 China launched an attack on Gac Ma Island – one of the larger Spratly Islands which was formerly under Vietnamese military control – killing 64 Vietnamese soldiers in the last violent conflict between the two nations.

“We are here to commemorate our soldiers killed by Chinese,” teacher Pham Toan said in front of a statue of Ly Thai To – the founder of Hanoi and a nationalist figurehead.

“Their sacrifice has been long forgotten by Vietnamese authorities,” Toan added, referring to activist claims that the communist authorities do not sufficiently commemorate the battle.

Vietnam’s communist leadership’s handling of its delicate relationship with China – which is the country’s largest trading partner – is a frequent flashpoint for domestic criticism of Vietnam’s authoritarian government.

Watched by dozens of plain-clothed security officers, the activists played patriotic music and waved Vietnamese flags near the central Hoan Kiem lake in Hanoi.

Dozens of activists laid floral wreaths covered with black ribbons that read “the people will never forget” at the statue of Ly Thai To.

The protest lasted about an hour. Vietnam’s tightly controlled state media covered the anniversary but not Monday’s protest. There was no official comment from the government.

Beijing’s increasingly assertive stance in contested waters has triggered public anger and rounds of protests in authoritarian Vietnam where the demonstrations are sometimes forcefully broken up.

The Spratlys are claimed by Hanoi but controlled by Beijing, which has ramped up activity in the area by rapidly building artificial islands, including airstrips said to be capable of hosting military jets.

Rioting broke out in Vietnam after Beijing sent an oil rig into contested waters in 2014, and at least three Chinese people were killed.

Apart from China and Vietnam the Spratly Islands are claimed in whole or in part by the Philippines, Malaysia, Brunei and Taiwan.

Agence France Presse - March 14, 2016