At least eight blasts were reported. Three churches in Negombo, Batticaloa and Colombo’s Kochchikade district were targeted during Easter services.
The Shangri-La, Kingsbury, Cinnamon Grand and a fourth hotel, all in Colombo, were also hit.
A curfew has been imposed from 18:00 to 06:00 local time (12:30-00:30 GMT). Seven arrests have been made.
The government also said there would a temporary block on the use of major social media networks.
No-one has yet claimed responsibility for the attacks but the defence minister said they were probably carried out by one group.
What’s the latest from the scene?
St Sebastian’s church in Negombo was severely damaged. Images on social media showed its inside, with a shattered ceiling and blood on the pews. Dozens of people are reported to have died there.
There were heavy casualties too at the site of the first blast in St Anthony’s, a hugely popular shrine in Kochchikade, a district of Colombo.
Among those killed in Colombo were at least nine foreign nationals, hospital sources told the BBC.
Hospital sources in Batticaloa said at least 27 people had died there.
A hotel official at the Cinnamon Grand, near the prime minister’s official residence, told AFP the explosion there had ripped through a restaurant, killing at least one person.
A seventh explosion was later reported at a hotel near the zoo in Dehiwala, southern Colombo, with police sources reporting two deaths. The zoo has been closed.
An eighth explosion was reported near the Colombo district of Dematagoda. Media say it was suicide bomber and that three people were killed during a police raid.
Colombo resident Usman Ali told the BBC there were massive queues as he joined people trying to donate blood.
He said: “Everyone had just one intention and that was to help the victims of the blast, no matter what religion or race they may be. Each person was helping another out in filling forms.”
I’ve spoken to several priests who were in the church and they were really shocked, as were the police officers.
It was a well-planned, co-ordinated attack but I spoke to the security chief who was there and officials believe it’s too early to say who is behind it.
After the Tamil Tigers were defeated in 2009, Sri Lanka hasn’t really seen this kind of incident.