Updated

Around 100 anti-China protesters have gathered in Vietnam's capital to mark the 40th anniversary of a deadly naval battle between China and South Vietnam.

Police broke up Sunday's protest in Hanoi after around half an hour.

Protests are extremely rare in communist Vietnam and are typically quashed quickly by security forces. Dissidents and others accuse the government of not being tough enough against Beijing and its increasing assertiveness in pressing claims in the South China Sea.

The 1974 battle, in which 74 South Vietnamese soldiers died, followed China's occupation of the Paracel islands. It's especially sensitive because the North Vietnamese government didn't counter the Chinese move, or even acknowledge force was used. At the time, Beijing was giving North Vietnam arms and money to fight the U.S. and South Vietnam.