Police spokesman Ruwan Gunasekara said the situation has been brought under control. He said the violence started as a drunken, private brawl but refused to name parties involved.

The Sri Lankan government also blocked some social media sites overnight, including Facebook and WhatsApp, "in order to control the situation," the information department director Nalaka Kaluwewa said. The block was lifted early Monday.

The clash in the seaside town of Negombo is the first reported since the Easter bombings by Islamic extremists two weeks ago that killed more than 250 people.

A state of emergency has been in place since then, with warnings that more attacks are possible. Catholic churches were closed for a second weekend, and Muslims are under security surveillance and subjected to hate comments on social media.

Archbishop of Colombo Cardinal Malcolm Ranjith in a video message circulated on social media appealed for calm.

"So far we have dealt with our problems with patience and wisdom and I ask everyone to continue in that manner," he said

Military spokesman Sumith Atapattu said Sunday that several people had been injured in clashes in Negombo, where St. Sebastian's Church was targeted in the attacks carried out by bombers who had pledged support for the Islamic State group.

Ethnic clashes aren't new to Sri Lanka. A civil war between rebels from the minority Tamil community and the Buddhist Sinhalese-majority government ended in 2009.

Most of Sri Lanka's majority ethnic Sinhalese are Buddhists, but Negombo has a majority Sinhalese Catholic community.