Bomb blasts ripped through churches holding Easter services and rocked upscale hotels in Sri Lanka on Sunday, killing at least 207 people and leaving more than 470 injured, prompting a curfew being declared nationwide, government authorities said.

A total of eight explosions had ripped through the country as of press time, with six blasts hitting in the morning and two in the afternoon, and the curfew was imposed from 6 pm Sunday to 6 am Monday, Xinhua News Agency reported.

The Sri Lankan government has also imposed a temporary ban on social media to prevent the spread of false information, Reuters reported.

Police confirmed that 35 foreigners died in the blasts, including British, Dutch and US citizens. Two Chinese nationals were among the dead, Xinhua reported, citing the Chinese embassy in Sri Lanka.

Sri Lankan Prime Minister Ranil Wickremesinghe condemned the attacks as "cowardly", and said the government was working to "contain the situation".

Agence France-Presse called it the worst act of violence in the South Asian nation since the end of Sri Lanka's civil war a decade ago.

The powerful blasts, six in quick succession and then two more a few hours later, wrought massive carnage as they occurred when hundreds of worshippers were gathered at churches to celebrate Easter Sunday.

Police spokesperson SP Ruwan Gunasekara said explosions were reported at St. Anthony's Church in the capital Colombo, and another at a church in Katana on the outskirts of the capital.

A third explosion was reported at a church in Batticaloa to the east.

Television footage also showed blasts occurred at three hotels－the Cinnamon Grand, Shangri-La and Kingsbury hotels, all in the capital, which took place following the church blasts.

The seventh explosion happened opposite the Dehiwala Zoo in Colombo, and the eighth, in a house in a northern suburb of the capital, which was caused by a suicide bomber who detonated his explosives when police entered the residence to search it, AFP reported.

Police urged the public to stay indoors and not gather at the explosion sites which had been sealed off.

The Chinese embassy in Colombo activated an emergency response mechanism immediately after the incident, and embassy officials visited injured Chinese nationals being treated in hospitals who were reportedly in stable condition.

World leaders have denounced the blasts. No group has yet claimed responsibility.

Russian President Vladimir Putin called the attacks "cruel and cynical", while voicing confidence that "the perpetrators and the masterminds of such crimes committed amid the Easter festivities will get the punishments they deserve".

British Prime Minister Theresa May said, "The acts of violence against churches and hotels in Sri Lanka are truly appalling, and my deepest sympathies go out to all of those affected at this tragic time".

Turkish President Recep Tayyip Erdogan condemned the attacks, calling them "an assault on all of humanity."

Indian Prime Minister Narendra Modi said his thoughts are with the bereaved families. "There is no place for such barbarism in our region," he tweeted.