Sri Lanka on Wednesday blocked access to Facebook and suspended internet services in a troubled central district after police warned that rioters were using social media to spread anti-Muslim sentiment.
The government declared an island-wide state of emergency Tuesday and imposed curfews across Kandy after days of rioting claimed at least two lives and left Muslim homes and businesses in ruins.
Schools were shut across Kandy, a hill station popular with tourists, as rioters defied curfews and clashed with police who used teargas to disperse the mobs.
A senior government source said Sri Lanka's telecoms regulator had asked internet providers to block access to Facebook and other social media platforms to stop the unrest spreading.
"This is a temporary measure and we will have the restrictions removed soon," a top official told AFP on condition of anonymity.
He said police had already identified anti-Muslim messages being shared on social networks, including a video posted by a hardline Buddhist monk urging violence against Muslims.
Authorities suspended internet access entirely to curfew-bound Kandy after discovering rioters were using online messaging services like WhatsApp to coordinate attacks on Muslim properties.
Sri Lankan telecoms providers said they would be blocking certain social networks following an order from the island's regulator.
"Access to certain social media sites and messaging platforms will be restricted with immediate effect until further notice," Sri Lanka's largest mobile phone provider Dialog said in a statement.
The internet blackout in Kandy, 115 kilometres (72 miles) east of Colombo, has also affected media organisations to get pictures and video footage from the region.
Censorship and media oppression was used widely by strongman president Mahinda Rajapakse, who for a decade in power ordered local internet providers to block anti-government sentiment online.
His successor President Maithripala Sirisena was elected in 2015 promising an end to draconian government restrictions, but some websites critical of the government remain blocked.