At least 290 people were killed and 500 more injured in eight coordinated explosions which took place around Sri Lanka on Easter Sunday morning.
Emergency powers are now to come into force from midnight on Monday as the authorities scramble to react to the bomb attacks.
The legal basis for the social media blocks is not known, but the emergency will allow police and the military extensive powers to detain and interrogate suspects without court orders.
Censorship monitoring organisation NetBlocks said it found Facebook, WhatsApp, Instagram, YouTube, Viber, Snapchat and Facebook Messenger to be blocked in Sri Lanka.
According to the country’s ministry of defence, the blocks will prevent the spread of disinformation and ease tensions following the attacks.
They said the blocks will remain until authorities have finished investigating a suspected international network behind the bombings.
Speaking to the Associated Press, NetBlocks’s executive director, Alp Toker, warned that the block could prove counter-productive.
“What we’ve seen is that when social media is shut down, it creates a vacuum of information that’s readily exploited by other parties.
“It can add to the sense of fear and can cause panic,” Mr Toker explained.