The seventh attack hit a hotel in the southern Colombo suburb of Dehiwala, according to AFP. Two police officers are said to have died in the explosions.
An eighth blast in Colombo has been reported by AFP, citing Sri Lankan police.
AFP said that the death toll includes at least 35 foreigners according to police.
Chinese state media say one Chinese citizen is among the dead. Earlier, China's embassy said four Chinese nationals were hospitalized and in stable condition. It is not clear if the deceased was among them. Portugal's Ministry of Foreign Affairs confirms that one victim was a Portuguese citizen.
A Sri Lanka state-run newspaper, the Daily News, reported that more than 500 people have been hospitalised with injuries caused by the blasts.
A police official, who spoke on condition of anonymity, told AFP at least 45 people had been killed in Colombo, where three hotels and a church were hit.
Another 67 were killed in an attack on a church in Negombo north of the capital, with another 25 dead at a church in the town of Batticaloa, in the east of the country.
President Maithripala Sirisena issued a statement calling for people to remain calm and support the authorities in their investigations, the BBC reported.
BREAKING: Reports of another explosion in Sri Lanka, following a series of bomb attacks earlier on Sunday which killed at least 156 people, and injured over 400 more.
PM Ranil Wickremesinghe said: "I strongly condemn the cowardly attacks on our people today. I call upon all Sri Lankans during this tragic time to remain united and strong."
On Twitter, Finance Minister Mangala Samaraweera said the attacks appeared to be a "well-co-ordinated attempt to create murder, mayhem and anarchy" and had killed "many innocent people".
National Hospital spokesman Dr. Samindi Samarakoon said the nearly 300 wounded have been admitted to the capital Colombo's main hospital.
An official said they suspect the blasts at two churches were carried out by suicide bombers.
"Eighty people have already been admitted, and more are still coming in," an official at the Colombo National Hospital earlier told AFP on condition of anonymity.
Police said the blasts hit churches in the north of the capital and in the town of Negombo, just outside Colombo. There was also a blast at a church in the eastern town of Batticaloa.
The nature of the explosions was not immediately clear.
"A bomb attack to our church, please come and help if your family members are there," read a post in English on the Facebook page of the St Sebastian's Church at Katuwapitiya in Negombo.
Only around six per cent of mainly Buddhist Sri Lanka is Catholic, but the religion is seen as a unifying force because it includes people from both the Tamil and majority Sinhalese ethnic groups.
An image posted on Twitter of one of the hotel explosions.
A blast ripped through St. Anthony's Shrine in Colombo.
Alex Agileson, who was in the vicinity, said buildings in the surrounding area shook with the blast. He said a number of injured were carried in ambulances.
Sri Lankan Army soldiers secure the area around a church after a blast in Colombo, Sri Lanka. Photo / AP
A second explosion was reported at St. Sebastian's Church in Negombo, a Catholic majority town north of Colombo. The church has appealed for help on its Facebook page.
This image made from video, released by Derena TV shows women in despair after an explosion in Colombo, Sunday. Photo / AP
Sri Lankan security officials said they were checking for details. Police immediately rushed to both areas and sealed off the churches.
Strongly condemn the horrific blasts in Sri Lanka. There is no place for such barbarism in our region. India stands in solidarity with the people of Sri Lanka. My thoughts are with the bereaved families and prayers with the injured.
The Prime Minister of India condemned the attacks.
Narendra Modi tweeted: "Strongly condemn the horrific blasts in Sri Lanka. There is no place for such barbarism in our region. India stands in solidarity with the people of Sri Lanka."
Pakistan's foreign ministry condemned the explosions and terrorist attacks in Sri Lanka.
Ministry spokesman Mohammad Faisal said in a statement that the people and government of Pakistan stand by Sri Lanka after the Easter Sunday blasts.
Turkish President Recep Tayyip Erdogan condemned the Easter Sunday attacks, calling them "an assault on all of humanity."
In comments posted on Twitter, Erdogan offered his condolences to families of the victims and to the people of Sri Lanka.
It was the worst violence in the South Asian country since its civil war ended a decade ago.
Turkish Foreign Minister Mevlut Cavusoglu said: "Regardless of the motive, the attack in Sri Lanka is the same as the traitorous attack in Christchurch: cowardly, barbaric and cruel."
