World leaders have condemned a series of blasts in Sri Lanka that killed more than 150 people on Sunday, including dozens of foreigners -- with British, Dutch and American citizens believed to be among them.

Hospital sources also said Japanese citizens were among those injured by the bombs which ripped through high-end hotels and churches holding Easter services.

Here is a summary of the reactions:

Britain: 'Stand together' 

British Prime Minister Theresa May described the attacks as "truly appalling".

"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," she tweeted.

"We must stand together to make sure that no one should ever have to practise their faith in fear."

- The Netherlands: 'Terrible reports' -
"Terrible reports from Sri Lanka about bloody attacks on hotels and churches on this Easter Sunday," Dutch Prime Minister Mark Rutte tweeted after the attacks first emerged.

"Thoughts are with the victims and their relatives."

Australia: 'Terrorist attack' 

Prime Minister Scott Morrison said Australia was thinking of those killed in a "horrific terrorist attack".

"To the beautiful people of Sri Lanka, Australia sends its heartfelt sympathies and our prayers and our support -- and our offer to do whatever we can to support you in this terrible time of need," he said in a statement.

"At this time as Easter Sunday draws to a conclusion here in Australia, our heart goes out to those Christians and all of those other innocents who have been slaughtered today in this horrific terrorist attack."

New Zealand: 'Devastating' 

A month after dozens of Muslims were killed in a shooting at two mosques in Christchurch, New Zealand Prime Minister Jacinda Ardern described the attack as "devastating".

"New Zealand condemns all acts of terrorism, and our resolve has only been strengthened by the attack on our soil on the 15th of March. To see an attack in Sri Lanka while people were in churches and at hotels is devastating.

"New Zealand rejects all forms of extremism and stands for freedom of religion and the right to worship safely. Collectively we must find the will and the answers to end such violence."

Catholic Church in Holy Land: 'Solidarity' 

The Catholic Church in Jerusalem said the blasts were particularly sad as they "came while Christians celebrate Easter".

"We pray for the souls of the victims and ask for speedy recovery of the injured, and ask God to inspire the terrorists to repent of their killing and intimidation," the statement said.

"We also express our solidarity with Sri Lanka and all its inhabitants in their various religious and ethnic backgrounds."

European Union (EU): 'Horror and Sadness'

EU commission chief Jean-Claude Juncker expressed his "horror and sadness" after the deadly string of Easter Sunday attacks across Sri Lanka.

"It was with horror and sadness that I heard of the bombings in Sri Lanka costing the lives of so many people," Juncker said on Twitter, adding that the European Union stood ready to help.

"I offer my heartfelt condolences to the families of the victims who had gathered to worship peacefully or come to visit this beautiful country," Juncker said.

EU foreign policy chief Federica Mogherini said the attacks marked "a truly sad day for the country and for the world".

"Such acts of violence on this holy day are acts of violence against all beliefs and denominations, and against all those who value the freedom of religion and the choice to worship," she added in a statement.

Archbishop of Paris

Archbishop of Paris Michel Aupetit tweeted: "Why so much hate on this day when we celebrate love? On this Easter day, we are in communion with our murdered brethren of Sri Lanka.''

Aupetit celebrated Easter Mass for worshippers displaced from normal services at Notre Dame because of Monday's fire.

A soldier and several police guarded the building. It was unclear whether the extra security was linked to the Sri Lanka attack, but parishioner Monique Pigere said "I understand why'' security is needed, lamenting the "terrible'' news.

Bahrain, Qatar and the United Arab Emirates

Bahrain, Qatar and the United Arab Emirates all issued statements via their foreign ministries over the attack.

The UAE called upon ``the international community to close ranks and uproot the scourge of terrorism in order to ensure international peace and security.''

Qatar said it wanted to stress its ``its firm stance on rejecting violence and terrorism.''

Bahrain, meanwhile, said ``these acts of terrorism are incompatible with religious principles and human and moral values.''

The series of blasts at three churches and three luxury hotels killed at least 138 people.

It's the worst spout of violence in Sri Lanka since the South Asian country's bloody civil war ended a decade ago.

Russian President Vladimir Putin

In a telegram of condolences sent to his Sri Lankan counterpart, the Russian President Vladimir Putin said Moscow remains a ``reliable partner of Sri Lanka in the fight against international terrorism.''

He added that the Russians ``share the grief of the relatives of those killed and wish a quick recovery to all those who were wounded'' after the Easter Sunday blasts that killed at least 138 people.

Putin voiced confidence that ``the perpetrators and the masterminds of such a cruel and cynical crime committed amid the Easter festivities will take the punishment they deserve.''

Turkish President Recep Tayyip Erdogan

In comments posted on Twitter, Turkish President Recep Tayyip Erdogan offered his condolences to families of the victims and to the people of Sri Lanka.

The near simultaneous attacks against three churches and three luxury hotels killed at least 138 people, according to a security official. 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.''

He was referring to last month's attacks against two mosques in New Zealand during Friday prayers that killed 50 people.

Pakistan's Foreign Ministry

Pakistan's Ministry spokesman Mohammad Faisal said in a statement that the people and government of Pakistan stand by Sri Lanka after the Easter Sunday blasts that killed at least 138 people.

Pakistan and Sri Lanka enjoy close relations. Pakistan helped train Sri Lankan army officers in the civil war battle against Tamil rebels.