The death toll from the blasts that have hit Sri Lanka on Sunday rose to 290, and there are more than 500 injured, according to local media, quoting hospital sources.
The Sri Lanka Tourism Development Authority said in a statement that 32 foreigners from China, the United States, Britain and Belgium were among the dead.
The police said that seven suspects were arrested and that investigations are under way.
Police spokesman Ruwan Gunasekara said that security was tightened across the country and a mandatory curfew was imposed with no end date.
The police recovered a vehicle that was used by one of the suspects to transport the explosives in the capital, Gunasekara said.
Defense Minister Ruwan Wijewardene said that almost all the explosions in Colombo were carried out by suicide bombers from "extremist groups".
The police said that, at the moment, they cannot disclosure who is behind the attacks.
Eight explosions occurred in Sri Lanka on Sunday as hundreds of worshipers gathered in churches to celebrate the Easter.
Gunasekara said that the explosions were reported in St. Anthony's Church in Kochchikade, the capital of Colombo, and in St. Sebastian's Church in Negombo, Colombo's suburb, on Sunday morning.
The third explosion took place at the Zion Church in the eastern village of Batticaloa.
The explosions also hit three luxury hotels in Colombo -Cinnamon Grand, Shangri-La and Kingsbury, while on Sunday afternoon an explosion was confirmed at a hotel in front of a zoo in Dehiwala in Colombo and another one in a residential development in Dematagoda, also in the capital.