A series of coordinated bomb blasts at churches and hotels across Sri Lanka killed more than 200 people and left hundreds more injured on Easter Sunday in one of the worst bouts of violence in the island nation since civil war ended a decade ago.

Four luxury hotels and three Catholic churches were among the highly populated areas that were targeted, according to the Associated Press. Officials told the AP that at least two of the blasts were carried out by suicide bombers.

Late Sunday, Sri Lanka’s Defense Minister Ruwan Wijewardena said authorities apprehended several people suspected of being involved in the attacks, according to the Associated Press. Three police officers were reportedly killed during operations to arrest the suspects.

A further improvised device was found at Bandaranaike International Airport by the Sri Lankan Air Force overnight Sunday. “A PVC pipe which was six feet in length containing explosives in it was discovered,” Air Force Spokesman Gihan Seneviratne told Sri Lanka’s main newspaper the Sunday Times.

Two senior intelligence officials told The Daily Beast that a Sri Lankan police official had alerted security officials in an advisory ten days ago about a threat on churches though it remains unseen what, if any, safety measures were taken to protect worshipers. The document, which has been reviewed by The Daily Beast is written in Sinhala, but is dated April 11 and clearly states in English in all caps, “Information of an alleged plan attack.”

Sri Lanka’s prime minister, Ranil Wickremesinghe, said he had not been informed, underscoring tensions within the government, the New York Times reported. No one has yet claimed responsibility for the calculated attacks.

Both the Associated Press and AFP quoted local Sri Lankan intelligence officials that they had received warnings that “terrorist elements, including the radical Islamic organization NTJ, would carry out a suicide attack in certain churches during Easter.”

U.S. Secretary of State Mike Pompeo issued a statement Sunday confirming that “several Americans” had been killed in the attacks. “While many details of the attacks are still emerging, we can confirm that several U.S. citizens were among those killed,” he wrote in a statement. “These vile attacks are a stark reminder of why the United States remains resolved in our fight to defeat terrorism.”

Officials told the Associated Press that at least nine foreigners are among those killed in Colombo, including two people who are dual citizens of the United States and the U.K. At least one American is among those reported missing, the news site said citing the Sri Lankan Ministry of Foreign Affairs. The dead include one Portuguese citizen and two U.K. citizens, the ministry said.

Chinese State Media has confirmed death of one of its citizens, per the AP. All of the foreigners were killed in attacks on hotels.

Emergency officials were still combing through the bomb sites for victims as night set in Sunday, but more tourists and foreign nationals are considered to be among the dead.

The New York Times reports that the deadliest attack occurred at 8:45 a.m. at the St. Sebastian Catholic Church in the city of Negombo about 20 miles from the capital city of Colombo. Survivors posted photos on social media and described seeing bodies blown to bits, with flesh splattered on the church walls.

“It was a river of blood,” a witness named N. A. Sumanapala, t0ld the Times. “The priest came out and he was covered in blood.”

The Catholic churches of St. Anthony’s Shrine in Colombo and the Zion Church in Batticaloa on the eastern side of the island were also bombed, according to reports.

Pope Francis, who visited the country four years ago to minister to the island nation’s Christian minority, expressed his condolences in his Easter Sunday mass in St. Peter’s Square in Rome. “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 said. “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 dramatic event.”

Local media showed images of damage at the Cinnamon Grand, Shangri-La and Kingsbury hotels. One report showed the second-floor restaurant of the Shangri-La gutted.

Sri Lanka has not seen such violence since the end of a 26-year civil war that ended over a decade ago. Then, rebels from the Tamil Tigers sought independence from the country’s Sinhala Buddhist majority.

Sri Lanka’s prime minsiter Ranil Wickremesinghe called for calm on Twitter. “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 wrote. “Please avoid propagating unverified reports and speculation. The government is taking immediate steps to contain this situation.”

The BBC reported that British nationals were among the injured. Prime Minister Theresa May called the attacks “truly appalling” adding “no one should ever have to practice their faith in fear”.

U.S. President Donald Trump also tweeted his condolences, “The United States offers heartfelt condolences to the great people of Sri Lanka. We stand ready to help!”

The attacks sent officials around the world into high gear taking precautions at churches in preparation for Easter celebrations.

A spokesperson for the NYPD confirmed to The Daily Beast that the department has ramped up domestic security measures in the wake of the attacks, and that officers will be visiting all houses of worship, with a focus Sunday on those offering Easter services.

—With reporting from Pervaiz Shallwani and Victoria Albert