HANOI (Reuters) - Up to 300 people shouting "Down with China" marched to the Chinese embassy in Vietnam on Sunday to protest against what they see as Chinese violations of Vietnam's sovereignty in the disputed South China Sea.

Tension between Vietnam and China has been on the rise since last month when Vietnam said Chinese patrol boats harassed a Vietnamese oil-exploration ship conducting a seismic survey 120 km (80 miles) off Vietnam's south-central coast.

The two countries, which fought a brief but intense war on their land border in 1979, have exchanged accusations and re-staked long-standing claims of sovereignty over maritime territory which covers important shipping routes and is thought to hold large, untapped oil and gas reserves.

Public protests are rare in Vietnam but as well as the procession of banner-waving people in the capital, images posted online showed about 1,000 people marching in what appeared to be a similar protest in Ho Chi Minh City, Vietnam's commercial hub.