At least 207 people were killed and more than 500 were injured in Sri Lanka on April 21 as multiple coordinated explosions hit several locations including hotels and churches in the capital where worshippers attended Easter services.
At least six explosions were reported in the morning. Two more blasts were reported later in the day.
Some reports suggested that the attacks had been carried out by suicide bombers.
The defense minister said seven suspects linked to the blasts have been arrested.
Three churches hit were in the north of the capital, the town of Negombo, just outside Colombo, and another in Batticaloa, 250 kilometers east of the capital.
St. Sebastian's Curch at Katuwapitiya in Negombo posted pictures of destruction inside the church on its Facebook page, showing blood on pews and the floor, and requested help from the public.
At least 50 people are reported to have died there.
Three other explosions were reported in five-star hotels, according to police.
At least 27 foreigners were among the dead, the country's foreign minister said.
The violence is reported to be the worst since Sri Lanka's bloody civil war ended a decade ago.
Finance Minister Mangala Samaraweera said in a tweet that the attacks appeared to be a "well-coordinated attempt to create murder, mayhem and anarchy" and had killed "many innocent people."
Government minister Harsh de Silva wrote on Twitter that he had seen “horrible scenes” after the explosions and that there were “many casualties including foreigners.”
There were no immediate claims of responsibility.
President Maithripala Sirisena has issued a statement calling for people to remain calm and support the authorities in their investigations.
A curfew was imposed following the attacks and officials said major social-media networks and messaging apps, including Facebook and WhatsApp, were blocked inside the country to prevent misinformation and rumors.
Security in the capital and the airport has been stepped up following the incidents.
World leaders have condemned the attacks. Pope Francis expressed his sadness and said he stood with the victims of "such cruel violence."
U.S. President Donald Trump tweeted: “The United States offers heartfelt condolences to the great people of Sri Lanka. We stand ready to help!”
Only 7 percent of the population in Sri Lanka are Christians. Most are Buddhists.
Based on reporting by AFP, Reuters, dpa, AP, The Washington Post, and Sundaytimes.lk