Social media networks and messaging apps are being temporarily blocked in Sri Lanka.
The government's limiting access to services including Facebook, Snapchat, Instagram, YouTube and WhatsApp.
The move follows attacks on mosques and Muslim-owned businesses in some of the worst unrest since the Easter bombings by Islamist militants.
Dozens of people threw stones at mosques and Muslim-owned stores on Sunday (May 12).
And a man was beaten in the Christian-majority town of Chilaw in a dispute that started on Facebook, sources told Reuters.
Authorities said they arrested the 38-year-old author of a post.
People claimed his online comment "1 day u will cry" was interpreted as threatening violence.
Police also took in a group of men for allegedly attacking Muslim-owned businesses, a police source told Reuters, before people in the mostly Buddhist district demanded their release.
A police curfew was imposed during the night.
The flare-up comes three weeks after Sri Lankan Islamist bombers blew themselves up in four hotels and three churches, killing more than 250 people.
Since then, Muslim groups say they have received dozens of complaints about people being harassed.
Other communities say they fear the government, which failed to act on successive warnings about looming Islamist attacks, has not caught all potential militants.
Sri Lanka has used temporary bans on social media in a bid to deter misinformation and rumours.