(CNN) A wave of attacks in Sri Lanka left more than 250 people dead and hundreds more injured on Easter Sunday after a series of explosions tore through churches and hotels on what should have been a day of rest and worship.

By Sunday afternoon, there were eight blasts and the government had announced an island-wide curfew starting at 6 p.m. local (8:30 a.m. ET Sunday) until the following morning. Social media sites were also blocked as investigations took place.

"These are certainly acts of terror," the High Commissioner of Sri Lanka to the UK Manisha Gunasekera told CNN on Sunday.

"This is an attack against the whole of Sri Lanka because Sri Lanka is very multi-ethnic, multi-religious and multi-cultural country and the whole country comes together in celebration of Easter Sunday."

What happened?

There were almost simultaneous explosions on Sunday morning, which hit busy Easter services at churches in three separate cities.

Targets included St. Anthony's Shrine in Colombo, St. Sebastian's Church more than 22 miles north in Negombo, and the evangelical Zion Church in Batticaloa, 196 miles away from Colombo on Sri Lanka's east coast.

Additional explosions occurred on Sunday morning at high-end hotels in Colombo: the Cinnamon Grand, Shangri-La Hotel and The Kingsbury.

By the afternoon, a seventh and eighth blast occurred at a hotel in front of the Dehiwala Zoo in Dehiwala-Mount Lavinia and at a private house in Mahawila Gardens, in Dematagoda, while police officers conducted a house raid.

Four days after the coordinated attacks, the Sri Lankan Health Ministry revised the death toll, saying 253 people had died. That toll is significantly lower than the 359 initially reported to CNN by a Colombo police spokesman this week. The health ministry cited the condition of remains and the difficulty in identifying them for the discrepancy.

Who carried out the attacks?

It is still unclear who caused the attacks. What is known is at least seven people have been arrested in connection with the bombings and three police officers were killed during a house raid in connection to the attacks.

"The Colombo crime division... went to a house at [Mahawila Gardens] in Dematagoda, in relation to information received with regard to these hotels explosions," Police Spokesman Ruwan Gunasekara, said at a press conference.

"When crime division officials started questioning the people in the house, two explosions occurred, One sub inspector and two constables of police have been killed and one constable was taken to the national hospital with wounds," he added.

High Commissioner Gunasekera, told CNN they had information that the attacks were suicide bombings.

Who was targeted?

Sri Lanka's minority Christian community appeared to be the main target of the seemingly coordinated attacks. Christianity is a minority religion in Sri Lanka, accounting for less than 10% of the total population of 21.4 million.

According to census data, 70.2% of Sri Lankans identify as Buddhist, 12% Hindu, 9.7% Muslim, and 7.4% Christian.

It is estimated that 82% of Sri Lankan Christians are Roman Catholic

Tourists were also targeted in the attacks, Sri Lanka High Commissioner Gunasekera told CNN.

Photos: In pictures: Sri Lanka on alert as mourners bury blast victims A priest conducts a burial ceremony for victims of the Easter Sunday bombings in Negombo, Sri Lanka, on Wednesday, April 24. Hide Caption 1 of 39 Photos: In pictures: Sri Lanka on alert as mourners bury blast victims A woman who lost her husband and two children during the bombing at St. Sebastian's Church in Negombo yells toward the grave site during a mass burial on Wednesday. Hide Caption 2 of 39 Photos: In pictures: Sri Lanka on alert as mourners bury blast victims Military personnel talk with a police officer near the site where a package, believed to be a bomb, was detonated in a controlled explosion after being discovered in a nearby restaurant in Negombo on Wednesday, April 24. Hide Caption 3 of 39 Photos: In pictures: Sri Lanka on alert as mourners bury blast victims Members of a security task force search for explosives ahead of victims' mass burials in Negombo on Wednesday. Hide Caption 4 of 39 Photos: In pictures: Sri Lanka on alert as mourners bury blast victims On Tuesday, April 23, Harshani Sriyani weeps over the body of her daughter who was killed in the Easter Sunday bombings in Colombo. Hide Caption 5 of 39 Photos: In pictures: Sri Lanka on alert as mourners bury blast victims Funeral ribbons hang across a road leading to St. Anthony's Shrine on April 23. Hide Caption 6 of 39 Photos: In pictures: Sri Lanka on alert as mourners bury blast victims A man is supported as he follows a coffin during a mass funeral for bombing victims at St. Sebastian Church in Negombo, Sri Lanka, on Tuesday, April 23. Hide Caption 7 of 39 Photos: In pictures: Sri Lanka on alert as mourners bury blast victims A soldier stands guard next to members of the clergy during a mass funeral in Negombo on Tuesday. Hide Caption 8 of 39 Photos: In pictures: Sri Lanka on alert as mourners bury blast victims Coffins are carried to a grave during the mass funeral at St. Sebastian Church on April 23. Hide Caption 9 of 39 Photos: In pictures: Sri Lanka on alert as mourners bury blast victims A woman carrying an infant runs for safety after police found a suspicious vehicle parked in Colombo, Sri Lanka, on Monday, April 22, a day after several coordinated bombings across the country killed hundreds. Hide Caption 10 of 39 Photos: In pictures: Sri Lanka on alert as mourners bury blast victims Sri Lankan security forces stand at the site near St. Anthony's shrine in Colombo after they performed a controlled detonation of a suspicious van on Monday. Hide Caption 11 of 39 Photos: In pictures: Sri Lanka on alert as mourners bury blast victims Smoke rises from the area where a van exploded on Monday near St. Anthony's shrine in Colombo. Hide Caption 12 of 39 Photos: In pictures: Sri Lanka on alert as mourners bury blast victims Security personnel stand guard outside St. Anthony's Shrine on Monday, a day after the church was hit in a series of bomb blasts targeting churches and luxury hotels in Sri Lanka. Hide Caption 13 of 39 Photos: In pictures: Sri Lanka on alert as mourners bury blast victims Relatives weep near the coffin of 12-year-old victim Sneha Savindi, who was killed in the Easter Sunday bombing at St. Sebastian's Church in Negombo, Sri Lanka. Hide Caption 14 of 39 Photos: In pictures: Sri Lanka on alert as mourners bury blast victims Police and forensics officials inspect the interior of St. Sebastian's Church in Negombo on Monday. Hide Caption 15 of 39 Photos: In pictures: Sri Lanka on alert as mourners bury blast victims Shoes and belongings of victims are collected as evidence at St. Sebastian's Church in Negombo on April 22. Hide Caption 16 of 39 Photos: In pictures: Sri Lanka on alert as mourners bury blast victims A man mourns after viewing the body of a dead relative killed in the bomb explosion at St. Anthony's Church in Colombo on Sunday, April 21. Hide Caption 17 of 39 Photos: In pictures: Sri Lanka on alert as mourners bury blast victims Blood stains are seen on a statue of Jesus Christ after a bomb blast inside a church in Negombo, on Sunday. Hide Caption 18 of 39 Photos: In pictures: Sri Lanka on alert as mourners bury blast victims A woman is in tears after a deadly bomb blast at St. Anthony's Shrine in Sri Lanka's capital, Colombo, on Sunday. Hide Caption 19 of 39 Photos: In pictures: Sri Lanka on alert as mourners bury blast victims Security personnel and investigators sift through debris outside Zion Church in Batticaloa. Hide Caption 20 of 39 Photos: In pictures: Sri Lanka on alert as mourners bury blast victims A man holds up a blood-stained photograph as people wait to identify the bodies of their loved ones in front of St. Anthony's Church. Hide Caption 21 of 39 Photos: In pictures: Sri Lanka on alert as mourners bury blast victims Relatives of a victim of the attacks react at the police mortuary in Colombo. Hide Caption 22 of 39 Photos: In pictures: Sri Lanka on alert as mourners bury blast victims Sri Lankan hospital workers and soldiers stand at the door to a morgue following a blast in a church in Batticaloa. Hide Caption 23 of 39 Photos: In pictures: Sri Lanka on alert as mourners bury blast victims A Sri Lankan Air Force helicopter flies over a house suspected to be a hideout of militants following a shootout in Colombo. Hide Caption 24 of 39 Photos: In pictures: Sri Lanka on alert as mourners bury blast victims A view of damage near the Dehiwala zoo in Colombo. Hide Caption 25 of 39 Photos: In pictures: Sri Lanka on alert as mourners bury blast victims Relatives of bombing victims gather at a mortuary in Colombo. Hide Caption 26 of 39 Photos: In pictures: Sri Lanka on alert as mourners bury blast victims Colombo's Kingsbury Hotel was targeted by a blast. Hide Caption 27 of 39 Photos: In pictures: Sri Lanka on alert as mourners bury blast victims Relatives of a blast victim grieve outside a morgue in Colombo. Hide Caption 28 of 39 Photos: In pictures: Sri Lanka on alert as mourners bury blast victims Sri Lankan Special Task Force personnel gesture outside a house during a raid following an explosion at a property in the Orugodawatta district of Colombo. Hide Caption 29 of 39 Photos: In pictures: Sri Lanka on alert as mourners bury blast victims The interior of St. Sebastian's Church in Negombo, north of Colombo, shows damage from a bomb blast. Hide Caption 30 of 39 Photos: In pictures: Sri Lanka on alert as mourners bury blast victims Sri Lankan military members stand guard outside St. Anthony's Church following an explosion. Hide Caption 31 of 39 Photos: In pictures: Sri Lanka on alert as mourners bury blast victims Crime scene investigators inspect the scene of an explosion at the Shangri-La hotel in Colombo. Hide Caption 32 of 39 Photos: In pictures: Sri Lanka on alert as mourners bury blast victims Sri Lankan police officers clear the road as an ambulance drives through carrying injured from bomb blasts in Colombo. Hide Caption 33 of 39 Photos: In pictures: Sri Lanka on alert as mourners bury blast victims A bombing victim's relative weeps outside a hospital in Batticaloa, eastern Sri Lanka. Hide Caption 34 of 39 Photos: In pictures: Sri Lanka on alert as mourners bury blast victims Priests view blast debris outside St. Anthony's Shrine. Hide Caption 35 of 39 Photos: In pictures: Sri Lanka on alert as mourners bury blast victims Sri Lankan security personnel keep watch outside St. Anthony's Shrine. Hide Caption 36 of 39 Photos: In pictures: Sri Lanka on alert as mourners bury blast victims Security forces inspect the inside of St. Anthony's Shrine after Sunday's attack. Hide Caption 37 of 39 Photos: In pictures: Sri Lanka on alert as mourners bury blast victims Sri Lankan military officers stand guard in front of St. Anthony's Shrine. Hide Caption 38 of 39 Photos: In pictures: Sri Lanka on alert as mourners bury blast victims A relative of a victim of an explosion at St. Anthony's Shrine reacts outside the police mortuary in Colombo. Hide Caption 39 of 39

Among the hundreds killed were about 30 foreigners, according to government officials. The toll included two Turkish citizens, one Dutch national and two Chinese cousins.

Some British citizens were also "caught in the blast," said British High Commissioner to Sri Lanka, James Dauris.

The tourism industry is a major source of income for the country, which turned itself into a popular tourist destination a decade since the end of its civil war. Last year, it won the title of best place in the world to visit in 2019 by travel guide publisher Lonely Planet.

Update: This story has been updated to reflect the death toll has been revised by the Sri Lankan Health Ministry.