At least six explosions have been reported. Three churches in Kochchikade, Negombo and Batticaloa were targeted during Easter services.
The Shangri La, Cinnamon Grand and Kingsbury hotels, all in Colombo, were also hit.
Easter Sunday is one of the major feasts in the Christian calendar.
Images on social media showed the inside of one of the churches - St Sebastian's in Negombo - with a shattered ceiling and blood on the pews.
Sri Lankan media report that foreign tourists may be among the casualties.
Read more at:
https://www.bbc.com/news/world-asia-48001720