Easter Day bomb blasts at three Sri Lankan churches and four hotels killed more than 200 people and wounded more than 450, 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.

What happened?

The powerful blasts – six in quick succession and then two more hours later – wrought devastation, including at the capital’s well-known St Anthony’s Shrine, a historic Catholic Church.

The three hotels hit in the initial attacks were the Shangri-La Colombo, Kingsbury Hotel in Colombo and the Cinnamon Grand Colombo.

The first six explosions were all reported within a short period in the morning just as church services were starting. Hours later there were two further attacks in the outskirts of Colombo.

Police said at least three of the attacks were carried out by suicide bombers.

Who were the victims?

The death toll rose rapidly to more than 200 and was expected to rise further still. There were hundreds of people injured in hospitals.

The secretary of state Pompeo condemned the attack in a statement Sunday morning and said “several U.S. citizens were among those killed.”

“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,” Pompeo said. “The U.S. Embassy is working tirelessly to provide all possible assistance to the American citizens affected by the attacks and their families.”

There were five British citizens killed in the attack, Sri Lanka’s ministry of foreign affairs stated.

One Dutch person was among those killed, Dutch foreign minister Stef Blok said in a statement.

Who was behind the attacks?

Seven suspects were arrested on Sunday afternoon, Sri Lanka’s defense minister said.

The nature of the blasts was not immediately clear and there were no immediate claims of responsibility.

Sri Lanka’s police chief Pujuth Jayasundara had issued an intelligence alert to top officers 10 days ago, warning that suicide bombers planned to hit “prominent churches”.

“A foreign intelligence agency has reported that the NTJ (National Thowheeth Jama’ath) is planning to carry out suicide attacks targeting prominent churches as well as the Indian high commission in Colombo,” the alert said.

The NTJ is a radical Muslim group in Sri Lanka that was linked last year to the vandalism of Buddhist statues.

How did Sri Lanka react?

The government beefed up security and imposed an immediate and indefinite curfew across the country. It also put in place a “temporary” ban on social media platforms “in order to prevent incorrect and wrong information being spread”.

Security at Colombo’s airport was also enhanced, according to Sri Lankan Airlines, which advised its passengers to arrive four hours before their flights. It added that passengers with passports and tickets will be able to reach the airport during the curfew.

Embassies in Sri Lanka have warned their citizens to shelter in place.

Christians are an ethnic minority in Sri Lanka

The bombings came during church services on Easter Sunday, the most important holiday in the Christian calendar.

Sri Lanka is an ethnically diverse country with a predominantly Buddhist population. Nearly 70 percent of Sri Lankans are Buddhists, according to a 2012 census. Twelve percent are Hindu, nearly 10 percent are Muslim and seven percent are Christian.