Vietnamese activists shouting anti-China slogans have marked the 25th anniversary of a bloody naval battle with China with a rare public protest.

State media covered the anniversary, but didn't report on the small protest, held Thursday at a statue of a nationalist leader in Hanoi. Vietnam's one-party government is vulnerable to charges that it is not tough enough on China and doesn't usually allow open protests.

Around 20 people staged the brief demonstration, shouting slogans against Beijing.

The clashes in 1988 in the Spratly Islands in the South China Sea killed 64 Vietnamese troops. No Chinese were killed.

China's current assertiveness in pushing its territorial ambitions in the South China Sea is raising regional tensions. The Philippines, Brunei, Malaysia Taiwan and Vietnam all have claims in the waters.