Thirteen people were arrested and three officers were killed on Sunday as police sought those behind a rash of bombings at churches and hotels in Sri Lanka that killed more than 200 people, 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 spokesperson Ruwan Gunasekera told reporters in Colombo.

Those killed included 32 foreigners, following the near simultaneous and co-ordinated explosions that struck three churches and three luxury hotels, in one of the deadliest blasts in the country's history, government officials said.

U.S. Secretary of State Mike Pompeo said "several" Americans were among the dead. Global Affairs Canada said in a statement that it has "no reports of any Canadian citizens being affected" by the attacks.

Among the fatalities were three people from Denmark, two from Turkey, and one from Portugal, Sri Lankan officials said. There were also Chinese and Dutch among the dead, according to media reports. Five British people, two of whom had dual U.S. citizenship, and three Indians were killed, according to officials in those countries.

The eight explosions, some of which officials said were suicide bomb attacks, led to an immediate clampdown, with the government declaring a curfew from 6 p.m. to 6 a.m. local time and blocking access to major social media and messaging sites, including Facebook and WhatsApp.

SriLankan Airlines is telling passengers booked on flights out of the country that they will be able to fly despite the curfew.

Watch: Sri Lanka reels from a series of co-ordinated bomb attacks

Sri Lanka reels from a series of co-ordinated bomb attacks on several churches and luxury hotels on Easter Sunday. 0:40

Three of the blasts targeted St. Anthony's Church in Colombo, St. Sebastian's Church in the western coastal town of Negombo and another, the Zion church in the eastern town of Batticaloa around 8.45 a.m. local time as the Easter Sunday mass was in progress, a police spokesperson said.

Three other explosions were reported from the five-star hotels — the Shangri-La, the Cinnamon Grand and the Kingsbury in Colombo. Foreigners and locals who were injured in hotel blasts were admitted to the Colombo General Hospital.

Hours later, two more blasts occurred as police moved to Dematagoda on the outskirts of Colombo and occupants of a house apparently set off explosives to prevent being arrested. A police spokesperson said three police officers were killed when they went to question suspects following a tip.

Military spokesperson Brig. Atapattu said one of the two blasts occurred at a guesthouse in Dehiwala, south of the capital, killing at least two people.

A Sri Lankan police commando enters a house suspected to be a hideout of militants following a shoot out in Colombo, Sri Lanka on Sunday. Thirteen people were arrested and three officers were killed during raids in search of suspects following the attacks. (Eranga Jayawardena/Associated Press)

No claim of responsibility

There were no immediate claims of responsibility for the attacks in a country which was at war for decades with Tamil separatists until 2009, a time when bomb blasts in the capital were common.

Local Christian groups have said they faced increasing intimidation from some extremist Buddhist monks in recent years. 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.

Dead bodies of victims lie inside St. Sebastian's Church damaged in blast in Negombo, north of Colombo, Sri Lanka, on Sunday. (Chamila Karunarathne/Associated Press)

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.

In a sign that the attacks on three churches and four hotels could lead to communal violence, police reported on Sunday night that there had been a petrol bomb attack on a mosque in the northwestern district of Puttalum and arson attacks on two shops owned by Muslims in the western district of Kalutara.

Government had 'prior information'

The government has acknowledged that it had "prior information" of attacks on churches involving a little known local Islamist group but didn't do enough about it.

Most of the deadly attacks in the past in Sri Lanka were carried out by the Liberation Tigers of Tamil Eelam (LTTE) which ran a military campaign for a separate Tamil homeland in the northern and eastern provinces of the island nation for nearly 30 years. The Tamil movement collapsed in 2009 after the Sri Lankan Army killed its supreme leader Velupillai Prabhakaran.

Ruwan Wijewardena, Sri Lanka's defence minister, described what happened as an "unfortunate terrorist incident" and suggested the explosions were the work of religious extremists.

New video shows one of the explosions that rocked a church in Sri Lanka's capital Colombo on Easter Sunday. 0:50

The Archbishop of Colombo called for those responsible for the Easter Sunday blasts in Sri Lanka to be punished "mercilessly."

Cardinal Malcolm Ranjith urged Sri Lanka's government to launch a "very impartial strong inquiry" and punish those found responsible "mercilessly because only animals can behave like that."

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. Please avoid propagating unverified reports and speculation. The government is taking immediate steps to contain this situation. —@RW_UNP

Prime Minister Ranil Wickremesinghe was meeting top military officials and tweeted earlier Sunday that "the government is taking immediate steps to contain the situation."

He described the attacks as "cowardly" and called on the country to remain "united and strong."

Wickremsinghe acknowledged that the government had some "prior information of the attack," though ministers were not told.

He said there wasn't an adequate response and there needed to be an inquiry into how the information was used. He also said the government needs to look at the international links of a local militant group.

(CBC)

"Absolutely horrific news from Sri Lanka," Canadian Prime Minister Justin Trudeau tweeted. "Canada strongly condemns the heinous attacks on Christians at churches and hotels. Our hearts & thoughts are with the families & loved ones of those killed and all those injured."

The Canadian government updated its travel advisory for Sri Lanka to urge its citizens in the country to "exercise a high degree of caution."

A relative of a victim of the explosion at St. Anthony's Shrine, Kochchikade church, reacts at the police mortuary in Colombo. (Dinuka Liyanawatte/Reuters)

Pope Francis denounced the "cruel violence" of the Easter Sunday attacks in Sri Lanka and called for prayers for all those who are suffering from the bloodshed.

Francis added an appeal at the end of his traditional Easter Sunday blessing to address the massacre.

The U.S. condemns in the strongest terms the Easter morning terror attacks in Sri Lanka. These attacks demonstrate the brutal nature of terrorists whose sole aim is to threaten peace & security. We offer our deepest condolences and stand with the government & people of <a href="https://twitter.com/hashtag/SriLanka?src=hash&ref_src=twsrc%5Etfw">#SriLanka</a>. —@SecPompeo

Speaking from the loggia of St. Peter's Basilica, Francis said: "I want to express my loving closeness to the Christian community, targeted while they were gathered in prayer, and all the victims of such cruel violence."

He added: "I entrust to the Lord all those who were tragically killed and pray for the injured and all those who are suffering as a result of this."