ALUTHGAMA, Sri Lanka — In some of the worst religious violence in Sri Lanka in decades, three people have been killed and 78 injured in riots between Buddhists and Muslims in this southwestern coastal town after months of rising tensions, officials said Monday.

The riots on Sunday followed a protest march by a hard-line Buddhist group, Bodu Bala Sena, which is led in part by monks. Its name roughly translates as Buddhist Power Force. Shops and homes in the area, many of them owned by Muslims, were set ablaze and vandalized in violence that continued throughout the night. Mobs shouting anti-Muslim slogans and hurling gas bombs and stones advanced on a Muslim part of the village of Welipitiya, where men were protecting a mosque.

Three mosques and several Muslim prayer houses were set on fire, according to unofficial reports. “They fought us face to face for two hours,” said M. Hussein, a Muslim man involved in the fighting on Sunday night. “The police didn’t show up until after people were dead.” Police teams eventually appeared in the early hours of Monday to transport the dead and injured, Mr. Hussein said.

Muslim residents said Monday that their lives had changed forever. “They finished the Muslims in this area,” said M. Farina, who added that the police watched impassively Sunday evening as Buddhist mobs attacked Muslim shops and homes.