Easter Day bomb blasts at three Sri Lankan churches and four hotels killed 138 people and wounded more than 400, hospital and police officials said, following a lull in major attacks since the end of the civil war 10 years ago.
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, a police official told Reuters, 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. It was unclear whether there were any casualties in the hotels.
The first six explosions were all reported within a short period in the morning just as church services were starting.
Nine foreigners were among the dead, the officials said.
Early in the afternoon, police reported there had been two more explosions. One was at a hotel near the national zoo in the Dehiwela area near Colombo.
A witness told local TV he saw some body parts, including a severed head, lying on the ground near the hotel.
The other explosion was in a house in Colombo, authorities said.
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.
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.
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.
ATTACKS ON CHRISTIANS
One of the explosions was at St. Anthony's Shrine, a Catholic Church in Kochcikade, Colombo, a tourist landmark.
St. Sebastian's posted pictures of destruction inside the church on its Facebook page, showing blood on pews and the floor, and requested help from the public.
Last year, there were 86 verified incidents of discrimination, threats and violence against Christians, according to the National Christian Evangelical Alliance of Sri Lanka (NCEASL), which represents more than 200 churches and other Christian organisations.
This year, the NCEASL recorded 26 such incidents, including one in which Buddhist monks allegedly attempted to disrupt a Sunday worship service, with the last one reported on March 25.
Out of Sri Lanka's total population of around 22 million, 70 percent are Buddhist, 12.6 percent Hindu, 9.7 percent Muslim and 7.6 percent Christian, according to the country's 2012 census.
In its 2018 report on Sri Lanka's human rights, the U.S. State Department noted that some Christian groups and churches reported they had been pressured to end worship meetings after authorities classified them as "unauthorized gatherings".
The report also said Buddhist monks regularly tried to close down Christian and Muslim places of worship, citing unidentified sources.
Malcolm Cardinal Ranjith, the archbishop of Colombo, told local TV that the public should remain calm and asked authorities to bring those responsible for the attacks before the law. He also requested the public donate blood for the injured.
Education Minister Akila Viraj Kariyawasam announced that all schools would be closed on Monday and Tuesday.
The heads of major governments condemned the attacks. Indian Prime Minister Narendra Modi said "there is no place for such barbarism in our region". Turkish President Tayyip Erdogan said in a tweet that "this is an assault on all of humanity”.
Christians celebrate the resurrection of Jesus Christ on Easter Day after his death on the cross.