The demonstrators suspect the government deployed the dancers as a way to stop them from getting close to the statue and make their speeches inaudible. The few who tried to get close to the statue of Ly Thai To, the founder of Hanoi and a nationalist icon, were shooed away.
The protesters were marking the 35th anniversary of a bloody border war between China and Vietnam, where anger over Beijing's increasingly assertive territorial claims on islands in the South China Sea that Hanoi insists belong to it is already running high.
Relations with China, Vietnam's ideological ally and major trading partner, are a highly sensitive domestic political issue for Hanoi's rulers. They don't want anger on the street against China to spread to other areas of its repressive rule.
Nguyen Quang A, a well-known dissident, and others attending the rally in Hanoi on Sunday said the government deployed the dancers at the statue of Ly Thai To, and at another statue nearby, to prevent them gathering there. The tactic appeared to be part of a low-key approach to policing the event to avoid confrontation. There were scores of plainclothes security officers at the rally, but very few wearing uniform.
Mr Quang said he asked the dancers to stop for a few minutes but that they refused.
Last year the government organized old women to hold a street protest to prevent a visiting US government official from reaching a dissident's house, where he was due to talk to him about Hanoi's human rights record.
Around 70 people took part in Sunday's rally close to Hoan Kiem Lake in downtown Hanoi.
They shouted anti-China slogans, and took video and photos of each other to be posted on dissident blogs and Facebook pages. After around 90 minutes, they managed to lay their wreaths commemorating the Vietnamese dead in the war at a pagoda before dispersing.
Earlier anti-China protests in the capital have resulted in demonstrators being dragged into buses or scuffles. The government is keen to avoid such images spreading on social media because they make it seem it is defending China against nationalist anger, which is widespread among many Vietnamese.