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.
No group has yet said it was responsible.
There have been fears that Islamic State group fighters returning from the Middle East could pose a threat in the country.
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. At least 67 people are reported to have died there.
There were heavy casualties too at St Anthony’s 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.
No-one was expecting this
Rumours have been reported of more attacks and police have told people to stay inside their houses and remain calm. But there is some element of panic.
There is a heavy military presence in front of all major state buildings. No-one was expecting this, it was a peaceful Sunday morning – everyone was going to Easter prayers.
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 the attacks.
After the Tamil Tigers were defeated in 2009, Sri Lanka hasn’t really seen this kind of incident.
What have officials said?
President Maithripala Sirisena has issued a statement calling for people to remain calm and support the authorities in their investigations.
PM Ranil Wickremesinghe is chairing an emergency meeting. He said: “I strongly condemn the cowardly attacks on our people today. I call upon all Sri Lankans during this tragic time to remain united and strong.”
On Twitter, Finance Minister Mangala Samaraweera said the attacks appeared to be a “well-co-ordinated attempt to create murder, mayhem and anarchy” and had killed “many innocent people”.
Another minister, Harsha de Silva, described “horrible scenes” at St Anthony’s Shrine in Kochchikade, saying he had seen “many body parts strewn all over”.
What’s Sri Lanka’s recent history?
In the years since the end of Sri Lanka’s civil war in 2009, there has been some sporadic violence, with members of the majority Buddhist Sinhala community attacking mosques and Muslim-owned properties. That led to a state of emergency being declared in March 2018.
The civil war ended with the defeat of the Tamil Tigers, who had fought for 26 years for an independent homeland for the minority ethnic Tamils. The war is thought to have killed between 70,000 and 80,000 people.