Seven people were arrested and three police officers were killed during a raid on a house in Colombo on Sunday as the death toll from a rash of bombings at churches and hotels in Sri Lanka rose past 200, police and local media said.
"Altogether we have information of 207 dead from all hospitals. According to the information as of now we have 450 injured people admitted to hospitals," Police Spokesman Ruwan Gunasekera told reporters in Colombo.
The eight explosions, some of which officials said were suicide bomb attacks, led to an immediate clampdown, with the government declaring a curfew and blocking access to major social media and messaging sites, including Facebook and WhatsApp.
Defence Minister Ruwan Wijewardene said seven people have been arrested following the series of explosions.
At least three churches, three luxury hotels and a guesthouse were among the targets of the attacks.
The explosions, some of which officials said were suicide bomb attacks, led to an immediate clampdown, with the government declaring a curfew and blocking access to most major social media and messaging sites.
It was unclear when the curfew would be lifted.
More than 50 people were killed in St. Sebastian's gothic-style Catholic church in Katuwapitiya, north of Colombo with pictures showing bodies on the ground, blood on the pews and a destroyed roof.
Media reported 25 people were also killed in an attack on an evangelical church in Batticaloa in Eastern Province.
The three hotels hit were the Shangri-La Colombo, Kingsbury Hotel in Colombo and the Cinnamon Grand Colombo.
Local TV showed damage at the Cinnamon Grand, Shangri-La and Kingsbury hotels.
The Shangri-La's second-floor restaurant was gutted in the blast, with the ceiling and windows blown out. Loose wires hung and tables were overturned in the blackened space.
The foreign minister said at least 27 foreigners were among those killed.
There were no immediate claims of responsibility for the attacks in a country which was at war for decades with Tamil separatists until 2009 during which bomb blasts in the capital were common.
Prime Minister Ranil Wickremesinghe called a national security council meeting at his home for later in the day.
"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," he said in a Tweet.
"Please avoid propagating unverified reports and speculation. The government is taking immediate steps to contain this situation."
President Maithripala Sirisena said he had ordered the police special task force and military to investigate who was behind the attacks and their agenda.
The military had been deployed, according to a military spokesman, and security stepped up at Colombo's international airport.
Chinese state media report that a Chinese citizen has died in the Sri Lanka attacks, while four Chinese nationals were hospitalised.
Portugal's Ministry of Foreign Affairs also confirmed that one victim was a Portuguese citizen.
One Dutch person was also among those killed in the bomb attacks, Dutch foreign minister Stef Blok said.
Christian groups say they have faced increasing intimidation from some extremist Buddhist monks in recent years.
And last year, there were clashes between the majority Sinhalese Buddhist community and minority Muslims, with some hardline Buddhist groups accusing Muslims of forcing people to convert to Islam.
Out of Sri Lanka's total population of around 22 million, 70 per cent are Buddhist, 12.6 per cent Hindu, 9.7 per cent Muslim and 7.6 per cent Christian, according to the country's 2012 census.
The heads of major governments condemned the attacks.
Australian Associated Press