The government declared a curfew in Colombo and blocked access to social media and messaging sites, including Facebook and WhatsApp. It was unclear when the curfew would be lifted.

The government has acknowledged that it had "prior information" of attacks on churches involving a little known local Islamist group but didn't do enough about it. Attention is turning to an small Islamist group.

In a sign that the attacks could lead to communal violence, police reported on Sunday night there had been a petrol bomb attack on a mosque in the northwestern district of Puttalum and arson attacks on two shops owned by Muslims in the western district of Kalutara.

On Sunday afternoon, three police officers were killed during a security forces raid on a house in the Sri Lankan capital several hours after the attacks, many of which officials said were suicide bomb explosions. Police reported an explosion at the house.

Thirteen arrests have been made, all of whom are Sri Lankans, police said.

"Altogether, we have information of 207 dead from all hospitals. According to the information as of now we have 450 injured people admitted to hospitals," police spokesman Ruwan Gunasekera told reporters.

Government officials said 32 foreigners were killed and 30 injured in the explosions that tore through congregations and gatherings in hotels in Colombo, Negombo and Batticaloa.

They included five British people, two of whom had dual US citizenship, and three Indians, according to officials in those countries.

Also among the fatalities were three people from Denmark, two from Turkey, and one from Portugal, Sri Lankan officials said. There were also Chinese and Dutch among the dead, according to media reports.

There were no immediate claims of responsibility for the attacks in a country which was at war for decades with Tamil separatists until 2009, a time when bomb blasts in the capital were common.

Prime Minister Ranil Wickremsinghe acknowledged the government had some "prior information of the attack", though ministers were not told.

He said there wasn't an adequate response and there needed to be an inquiry into how the information was used. He also said the government needs to look at the international links of a local militant group.

French agency Agence France Presse reported it had seen documents showing Sri Lanka's police chief Pujuth Jayasundara issued an intelligence alert to top officers 10 days ago, warning that suicide bombers planned to hit "prominent churches". He cited a foreign intelligence service as reporting that a little-known Islamist group was involved.

A Sri Lanka police spokesman said he was not aware of the intelligence report.

Dozens were killed in one of the blasts at St. Sebastian's Gothic-style Catholic church in Katuwapitiya, north of Colombo. Gunasekera said the police suspected a suicide attack there. Pictures from the site showed bodies on the ground, blood on the church pews and a destroyed roof.

Local media reported 25 people were also killed in an attack on an evangelical church in Batticaloa in Eastern Province.

The hotels hit in Colombo were the Shangri-La, the Kingsbury, the Cinnamon Grand and the Tropical Inn near the national zoo.

The first six explosions were all reported within a short period in the morning just as church services were starting.

The explosion at the Tropical Inn happened later and there was an eighth explosion at the house that was the subject of the police raid in Colombo.

The military has been deployed, a military spokesman said, and security stepped up at Colombo's international airport.

Schools, universities and the Colombo Stock Exchange will be closed on Monday as the island state tries to recover from the attacks.

Australian Associated Press