The Sri Lankan government has declared a curfew with immediate effect, and shut down all major social media and messaging services.
"A curfew will be imposed until things settle down," junior defence minister Ruwan Wijewardene told reporters in Colombo.
Government officials said Facebook and WhatsApp have been blocked to prevent misinformation and rumours.
Nearly 140 people have been killed and more than 400 people wounded after eight bomb blasts ripped through churches and hotels in the island nation on Sunday.

Turkey to host Gaza meeting amid ceasefire concerns
Tanzania opposition says hundreds killed in vote protests
Turkey sentences 11 people to life in prison over ski resort hotel fire
China sends its youngest astronaut to 'Heavenly Palace' space station
Israel launches more strikes on Gaza overnight, testing fragile truce
Trump-Putin summit cancelled, FT reports
Houthis say 43 detained UN staff to face trial over Israeli attack
Hurricane Melissa leaves 49 dead in Caribbean, churns north
