At least 100 people protested Sunday in the Vietnamese capital against Chinese territorial claims in the South China Sea — the latest in a string of anti-China protests in Hanoi in the past two months.

Witnesses say police allowed flag-waving demonstrators to march, as they filmed the procession and redirected traffic to allow it to take place. Such protests are a rarity in authoritarian Vietnam, where public dissent is discouraged and normally punished.

China claims sovereignty over the entire sea, putting it at odds with Vietnam, the Philippines, Malaysia and Brunei, which claim waters adjacent to their shores. Both Hanoi and Manila claim Chinese naval vessels have interfered with natural gas and oil exploration in waters they claim as their exclusive economic zones.

The region is also home to one of the world's most heavily trafficked commercial shipping lanes.

The disputes dominated last month's annual meeting of the Association of Southeast Asian Nations, ASEAN, in Bali. ASEAN and China reached a preliminary deal on a set of guidelines that could eventually lead to a binding code of maritime conduct. But analysts say they do not expect any such accord in the immediate future.