Sri Lankan police have arrested 23 people in connection with a spate of mob attacks on Muslim communities that left one person dead and dozens of shops and mosques destroyed.

Key points: Tensions have been running high since the Easter Sunday suicide bombings

Tensions have been running high since the Easter Sunday suicide bombings Sri Lanka's Government has imposed a nationwide curfew and blocked social media

Sri Lanka's Government has imposed a nationwide curfew and blocked social media UN advisers are warning the retaliatory attacks on Muslims could escalate

Communal violence in the Indian Ocean island nation has worsened in recent days, following last month's Easter Sunday bombings that killed more than 250 people.

A Muslim man was hacked to death on Monday in violence in which members of the largely Buddhist majority ethnic Sinhalese attacked Muslim-owned shops and homes in the country's north-west, Rauff Hakeem, a Cabinet minister and leader of the Sri Lanka Muslim Congress, said.

With communal violence reported in the capital, Colombo, and surrounding areas in the country's west and north-west, the Government has imposed a nationwide curfew and temporarily blocked social media and messaging apps.

Mob attacks on Muslim communities in Sri Lanka have left one person dead and dozens of shops and mosques destroyed.

Soldiers in armoured vehicles are patrolling the towns hit by sectarian violence, and a police spokesman said the situation had now been brought under control.

Tensions have been running high in Sri Lanka since the April 21 attacks by militant Islamic suicide bombers who struck two Catholic churches, one Protestant church and three luxury hotels.

Islamic State claimed responsibility for the attacks, which were carried out by a local radicalised Muslim group.

Sri Lanka has a dark history of communal tensions. For more than a quarter century it was embroiled in civil war as Tamil Tiger rebels fought to create an independent state for ethnic minority Tamils.

Security forces have been deployed to restive areas across the country. ( Reuters: Dinuka Liyanawatte )

When the conflict ended 10 years ago, the United Nations estimated about 100,000 people had been killed.

The UN's Adama Dieng, an adviser on the prevention of genocide, and Karen Smith, an adviser on the responsibility to protect, are now warning the attacks on Muslims could escalate if not stopped immediately.

"The country is trying to move forward from a traumatic period of inter-ethnic armed conflict, but these attacks are pushing Sri Lanka backwards," they said in a statement.

"If not adequately dealt with, the recent violence has the potential to escalate even further."

Women mourn at the funeral for Mohamed Salim Fowzul Ameer, who was killed in the sectarian violence. ( Reuters: Dinuka Liyanawatte )

Cardinal Malcolm Ranjith, the archbishop of Colombo, appealed to the public to maintain the peace and patience they showed in the first days after the attacks.

He said he found no religious nuances in the violence but local-level politicians had been found in the mobs.

"I ask the political leaders to keep their followers under control. It is no heroism in attacking Muslims and damaging their property — true heroism is to control and overcome oneself," he said.

AP/Reuters