National Hospital spokesperson Dr. Samindi Samarakoon said almost 300 wounded were admitted to the capital's main hospital.
A source in the police bomb squad said that one of the explosions was at St Anthony's Church in Kochcikade, Colombo.
The blasts occurred at around 8.45 am (local time) as Easter Sunday masses were in progress, PTI quoted police spokesman Ruwan Gunasekera as saying.
The churches targeted were the St Anthony's Church in Kochchikade and the St Sebestian's Church in Katuwapitiya, Katana, as well as on in Batticaloa.
Police also reported explosions at the Shangri-La Hotel and Kingsbury Hotel.
"Eighty people have already been admitted, and more are still coming in", an official at the Colombo National Hospital said on condition of anonymity.
No group has immediately claimed responsibility for the explosions so far.
St. Sebastian's church posted pictures of destruction inside the church on its Facebook page, showing blood on pews and the floor, and requested help from the public.
A major deadly terror attack in Sri Lanka with five explosions are reported.
(AP Photo/Eranga Jayawardena) People gather outside St. Anthony's Shrine where a blast happened, in Colombo, Sri Lanka, Sunday, April 21, 2019.
Finance Minister Mangala Samaraweera, writing on his verified Twitter account, said the attacks had killed "many innocent people" and appeared to be a "well-coordinated attempt to create murder, mayhem & anarchy".
At least 80 people have been injured in the blasts as worshippers were attending Easter Sunday services, a hospital official said.
An emergency meeting has been called by Prime Minister Ranil Wickremesinghe in view of the blast and 200 troops of Army have been deployed in the affected area.
Some reporters of the Sri Lankan media have stated on Twitter that at least 25 people have been killed in the explosions and over 150 people have been injured and have been taken to the hospital. "I call upon all Sri Lankans during this tragic time to remain united and strong", he said in a Tweet.
Earlier, Wickremesinghe tweeted that "the government is taking immediate steps to contain the situation".
"Horrible scenes. I saw many body parts strewn all over".
"Please stay calm and indoors", he added.
"British nationals in Sri Lanka should follow the instructions of the local authorities and check FCO travel advice for updates".
A series of bomb blasts in Sri Lanka, now a seventh one in Dehiwela.
The horrifying Easter Sunday attacks come after a lull violence in the country since the end of the civil war 10 years ago.