Sri Lanka blasts: At least 290 people died in the serial blasts in Sri Lanka on Easter Sunday

Suicide bombers struck churches and hotels in Sri Lanka on Easter Sunday, killing at least 290 people in a highly coordinated attack targeting Christians and foreigners that left this island nation reeling.

No group claimed responsibility for the attacks, the deadliest violence here since the end of the civil war a decade ago.

Police arrested 13 people in connection with the bombings, and three police officers were killed during a raid at a suspect's home. Sri Lankan officials did not identify those arrested or discuss a motive for the attacks. At least 450 were injured in the attacks, according to a police spokesman.

Images of splintered pews and bloodstained floors played across local television screens Sunday as the enormity of the attacks, launched on the holiest day of the Christian calendar, became clear.

The dead included "several" Americans, Secretary of State Mike Pompeo said. He blamed "radical terrorists" for the attacks.

Prime Minister Ranil Wickremesinghe told reporters Sunday that some government officials had prior intelligence about the attacks but didn't act on it.

"Information was there," he said at a news conference. "This is a matter we need to look into."

A letter circulating on social media appeared to be a notice issued by a senior police official on April 11, warning of potential attacks on churches by a little-known Islamist extremist group. The letter could not be independently verified.

Sri Lanka is a predominantly Buddhist nation, but it's also home to significant Hindu, Muslim and Christian communities. A popular destination for tourists, the country has been largely peaceful since the end of its 26-year civil war.

While there has been intermittent conflict between religious groups - including threats to Christians - nothing remotely like Sunday's attacks had occurred here.

Blasts ripped through three churches in the cities of Colombo, Negombo and Batticaloa at about 8:45 a.m. as worshippers were gathering for services, police said. Bombers also struck three hotels and a banquet hall in Colombo, the capital.

Ruwan Wijewardene, Sri Lanka's defense minister, said the attacks were carried out by suicide bombers. Six of the attacks occurred between 8:45 and 9:30 a.m.

There was a seventh blast at a banquet hall about 2 p.m. and an eighth at the house raided by police around 2:45 p.m.

The deadliest attack was at St. Sebastian's Church in Negombo, a beach town about 22 miles north of Colombo. Negombo, known as "Little Rome," is dotted with Catholic churches. Officials reported at least 104 dead there.

Also targeted was St. Anthony's Shrine, Kochchikade, the largest Catholic congregation in Colombo, and Zion Church in the eastern city of Batticaloa.

At least 66 people were killed in Colombo and 28 in Batticaloa, officials said.

Bombers also struck three luxury hotels in Colombo. Two people at the Shangri-La Hotel described a powerful explosion that made the ground shake just before 9 a.m. Photos showed broken windows and shattered glass on a street next to the hotel.

Sarita Marlou, a guest at the hotel, wrote on Facebook that she felt the impact of the explosion in the hotel's flagship restaurant all the way up on the 17th floor. She described seeing pools of blood as she evacuated the hotel.

Also targeted were the ground-floor Taprobane restaurant at the Cinnamon Grand Hotel and the luxury Kingsbury Hotel.

Three police officers were killed in an altercation at a home in the Dematagoda area of Colombo, police said. They had gone there to interrogate someone.

At least 11 of the dead at National Hospital in Colombo were foreigners, including two who held U.S. and British citizenship, according to the Foreign Ministry. Other foreigners included three from Britain, three from India, two from Turkey and one from Portugal. The unidentified bodies of 25 people believed to be foreigners were at a government mortuary in Colombo.

Pompeo condemned the attacks "in the strongest terms."

"Attacks on innocent people gathering in a place of worship or enjoying a holiday meal are affronts to the universal values and freedoms that we hold dear, and demonstrate yet again the brutal nature of radical terrorists whose sole aim is to threaten peace and security," he said in a statement.

Sri Lankan authorities announced a nationwide curfew, effective immediately. They blocked Facebook and the messaging application WhatsApp in an attempt to halt the spread of false and inflammatory messages. Security was heightened at churches across the country, and the streets of Colombo grew quiet and deserted as the curfew took effect.

Wickremesinghe, the prime minister, condemned "the cowardly attacks on our people today" and urged the country to remain "united and strong."

The SITE Intelligence Group, which tracks extremist activity online, reported Sunday that Islamic State supporters were portraying the attacks as revenge for strikes on mosques and Muslims. Sri Lankan officials did not identify the perpetrators or the motivation behind the attacks.

Yousef Al-Othaimeen, the head of the Organization of Islamic Cooperation, "strongly condemned" the "cowardly attacks (on) innocent worshippers and civilians." The OIC represents 57 predominantly Muslim nations.

People in Sri Lanka expressed a sense of disbelief at the eruption of violence. Biraj Patnaik, South Asia director for the human rights group Amnesty International, said Sri Lanka has witnessed rising hostility toward Christians and Muslims in recent years, including repeated attempted to disrupt prayers at churches. But the scale of Sunday's attacks, he said, was "shocking and unprecedented."

The bombings were the worst violence to hit Colombo since 1996, when a blast at the country's central bank killed nearly 100 people. That attack was carried out by the Liberation Tigers of Tamil Eelam, or Tamil Tigers, which waged a war for a separate Tamil homeland in Sri Lanka's north for more than 30 years.

Messages of condolence and condemnation on Sunday poured in from around the world.

President Donald Trump tweeted: "The United States offers heartfelt condolences to the great people of Sri Lanka. We stand ready to help!"

Pope Francis during his Easter address called the attacks "horrendous" and expressed a "heartfelt closeness to the Christian community, attacked while gathered in prayer, and to all the victims of such a cruel act of violence."

"I entrust to the Lord all who so tragically died, and I pray for the wounded and all those who suffer because of this traumatic event," Francis said.

India strongly condemned what it called a "ghastly and heinous act" and said it stood with the people of Sri Lanka "in this hour of grief."

The Church of England posted a prayer for the people of Sri Lanka on Twitter.