Two Turkish engineers working on a project in Sri Lanka also died in the attacks, the English-language Daily Sabah newspaper reported.
Streets in the capital were mostly deserted, and many businesses remained shuttered as heavy police deployment continued in the country.
A Sri Lankan soldier stands guard near a vehicle explosion after the police tried to defuse a bomb near St. Anthony's Shrine in Colombo on Monday, a day after a series of bomb blasts targeting churches and luxury hotels in Sri Lanka.
The official said there could be additional explosives or potential suicide bombers. Two more blasts were reported in the afternoon. According to a memo issued by a high-ranking Sri Lankan police official to the country's Ministerial Security Division, Diplomatic Security Division, Judicial Security Division, and Security Divisions of Retired Presidents, a suicide attack being was planned in Sri Lanka by Mohammed Zaharan, leader of the National "Thawhith Jamaan".
Eight people have been arrested in connection with the attacks so far, the government confirmed without revealing their identities.
The president's office announced that it was invoking emergency powers starting midnight Monday - allowing police and the military to detain and interrogate suspects without court orders.
Media reports in India said the warning had come from Indian intelligence agencies.
Numerous victims were attending three Christian churches that were targeted - St. Anthony's Shrine in Colombo and St. Sebastian's Church in Negombo, 20 miles north of the capital, and Zion Church, an evangelical church located in the eastern coastal city of Batticaloa.
It’s official: Easter Monday hottest ever recorded in UK
It has been the hottest Easter Monday on record in all four nations of the United Kingdom , the Met Office has said. Britain could see a record-breaking Easter weekend , with temperatures on track to break national records.
Spokeswoman Amy Mills urged Canadians in Colombo, the nation's capital, to limit their movements, avoid impacted areas, and take direction from local authorities.
"This is by all accounts an intelligence failure". Last October, he was suddenly appointed prime minister by President Maithripala Sirisena, leading to a constitutional crisis.
Is this week's violence connected to the civil war in Sri Lanka that ended a decade ago?
Cabinet spokesman Rajitha Senaratne said, "We are very, very sorry". "In happiness - and sadness - we help each other out".
The death toll in a string of Easter bombings at churches and hotels in Sri Lanka was increased to 311, according to the state minister for defense, as the country marked a national day of mourning on Tuesday.
Most of those killed are thought to be Sri Lankan nationals but officials say at least 31 foreigners are among the dead including British, Indian, Danish, Saudi, Chinese and Turkish nationals.
"What these bombings potentially do is take it from inertia and political infighting and rudderlessness to a real fear of instability and a sense of a return to the bad old days", said Alan Keenan, a senior Sri Lanka analyst with the International Crisis Group based in London.
For Canadian MP Gary Anandasangaree, who fled Sri Lanka at the age of 10, the move was deeply distressing. Those killed include celebrity Sri Lankan chef Shantha Mayadunne and her daughter, who posted a photo of the family having Easter breakfast just before the explosion.