The Sri Lankan government has reimposed a ban on social media platforms in an effort to stop the spread of rumours after violence erupted between groups of civilians in Negombo, site of one of the Easter Sunday bombings.
The bombings by Islamist militants, which killed more than 250 people, have raised fears that Muslims could be targets of communal violence.
A curfew has been imposed in the Negombo area until 7am local time.
Meanwhile Sri Lankan police have discovered a 10-acre camp in the eastern town of Kattankudy, where Islamist militants linked to the deadly Easter attacks are believed to have practised shooting and bomb-making.
The walled terrain is nestled in a poor residential area on the outskirts of the home town of Zahran Hashim, who is believed to have been a key player in plotting the April 21 attacks.
Islamic State has claimed responsibility for the church and hotel bombings that killed more than 250 people.
The narrow, sandy plot is dotted with a cinderblock four-storey watchtower, as well as mango trees, a chicken coop and a goat shed.
“They wanted to show this place was normal. If someone comes to see, it looks like a farm. But what they were doing is terrorism,” said a senior police officer in the Batticaloa area.
Police found bullet holes in the wall on one side of the grounds, as well as long tubes suspected of holding bombs, the officer said on Sunday.
Two owners of the plot of land have been arrested, the officer said.