Terrorist attacks on two mosques in New Zealand — which killed at least 49 people on Friday — have sparked horror, revulsion and dismay around the world.

One of the gunmen — believed to be an Australian extremist — apparently livestreamed the deadly assault.

"It is clear that this can now only be described as a terrorist attack," said Prime Minister Jacinda Ardern, describing it as "one of New Zealand's darkest days".

Below are some of the main international reactions so far.

Muslims face 'mass killing'

"With this attack, hostility towards Islam that the world has been has been idly watching and even encouraging for some time, has gone beyond the boundaries of individual harassment to reach the level of mass killing," said Turkish President Recep Tayyip Erdogan.

"If measures are not taken right away, news of other disasters will follow this one ... I am calling on the world, in particular the West, to take quick measures," he said.

Related: 'Terrorism does not have a religion': Pakistan condemns New Zealand mosque shootings

Queen 'deeply saddened'

Queen Elizabeth II, New Zealand's head of state, said she was “deeply saddened” by the attacks on the two mosques.

“I have been deeply saddened by the appalling events in Christchurch ... At this tragic time, my thoughts and prayers are with all New Zealanders,” the Queen said in a message.

“Prince Philip and I send our condolences to the families and friends of those who have lost their lives,” she said, paying tribute to emergency workers and volunteers providing support to the injured.

Queen Elizabeth is the sovereign of New Zealand and 15 other separate realms including Britain, Australia and Canada.

Prince Charles, the heir to the throne of New Zealand, said he was “utterly horrified” by the “barbaric attacks”.

“It is beyond all belief that so many should have been killed and injured at their place of worship,” he said.

“This appalling atrocity is an assault on all of us who cherish religious freedom, tolerance, compassion and community. The people of New Zealand will never allow hate and division to triumph over these things they hold dear.”

Charles's sons and their wives also sent their sympathies in a message that ended with “Kia kaha”, meaning “be strong” in Maori.

“We have all been fortunate to spend time in Christchurch and have felt the warm, open-hearted and generous spirit that is core to its remarkable people,” said Prince William, his wife Kate, his younger brother Prince Harry and his wife Meghan.

"No person should ever have to fear attending a sacred place of worship.

“This senseless attack is an affront to the people of Christchurch and New Zealand, and the broader Muslim community. It is a horrifying assault on a way of life that embodies decency, community, and friendship.”

'Racist hatred'

German Chancellor Angela Merkel said she mourned "with New Zealanders for their fellow citizens who were attacked and murdered out of racist hatred while peacefully praying in their mosques. We stand together against such acts of terrorism".

French President Emmanuel Macron echoed Merkel's message, condemning an "odious attack" and saying France "stands against any form of extremism". France has increased security measures at mosques and other religious sites after the deadly attack.

NATO chief Jens Stoltenberg said the US-led alliance "stands with our friend and partner New Zealand in defence of our open societies and shared values".

'Warning on dangers of Islamophobia'

The secretary-general of the 57-nation Organization of Islamic Cooperation, Youssef al-Othaimeen, said the attack “served as a further warning on the obvious dangers of hate, intolerance, and Islamophobia”.

Al-Othaimeen called on New Zealand “to provide more protection to the Muslim communities living in the country”.

Read: Australia takes precautions after national carries out NZ mosque massacre

He also offered his condolences for those affected by the mass shooting.

'Senseless acts of violence'

Pope Francis denounced the “senseless acts of violence” in the Christchurch mosque shootings and prayed for the Muslim community and all New Zealanders.

He said he was “deeply saddened to learn of the injury and loss of life cause by the senseless acts of violence at two mosques in Christchurch, and he assures all New Zealanders, and in particular the Muslim community, of his heartfelt solidarity in the wake of these attacks”.

US President Donald Trump extended his "warmest sympathy and best wishes" to the people of New Zealand "after the horrible massacre in the mosques".

"49 innocent people have so senselessly died, with so many more seriously injured. The US stands by New Zealand for anything we can do. God bless all!"

'Heinous crime'

Dubai’s ruler, Sheikh Mohammed bin Rashid Al Maktoum, tweeted his condolences, noting that “on a day of peace like Friday and at a place of worship like the mosque, we witnessed the most heinous crime of religious hatred”.

Chief Palestinian negotiator Saeb Erekat said he extends his “prayers and tears” to the families of the victims. Erekat denounced the “use of religion for political ends” on Twitter, recalling past attacks targeting places of worship, including Israeli settler Baruch Goldstein’s massacre of Palestinian worshippers at the Ibrahimi Mosque in the West Bank city of Hebron, and the assault on a Pittsburgh synagogue last year.

Hamas, which rules the Gaza Strip, called the carnage in New Zealand “a heinous crime against worshippers in their mosques”.

'Do the necessary'

Malaysian Prime Minister Mahathir Mohamad said he hoped New Zealand "will arrest these terrorists and do the necessary under the law of the country".

Indonesian President Joko Widoyo, head of the world's largest Muslim country, said "we strongly condemn these kind of violent acts".

'Cruel attack'

"An attack against peaceful people gathering for prayer is shocking in its cruelty and cynicism," Russian President Vladimir Putin said.

"I hope that those involved will be severely punished," he said in a message to Arden.

'Sickening act of violence'

British Prime Minister Theresa May offered deepest condolences "after the horrifying terrorist attack in Christchurch. My thoughts are with all of those affected by this sickening act of violence".

London Mayor Sadiq Khan said: “London stands with the people of Christchurch in the face of this horrific terror attack. London will always celebrate the diversity that some seek to destroy.”

Khan sought to reassure Muslim communities in London following the attacks, saying that the Metropolitan Police would be visible outside mosques.

Explore: Facts about New Zealand's Muslim minority — a mere 1pc of the population

'Fanatics want to destroy society'

Spanish Premier Pedro Sanchez said his thoughts were with the victims, families and government of New Zealand after attacks by "fanatics and extremists who want to destroy our societies".

'Harrowing news'

"Harrowing news from New Zealand overnight" said EU Council president Donald Tusk. "The brutal attack ... will never diminish the tolerance and decency that New Zealand is famous for."

Japan said it stands by the people of New Zealand.

Chief Cabinet Secretary Yoshihide Suga, in a regular news conference on Friday, expressed “heartfelt condolences” to the shooting victims and their families, while extending sympathy for the injured.

Suga expressed “solidarity with the people of New Zealand.”

'Painful memories'

Norwegian Prime Minister Erna Solberg urged the international community to combat all forms of extremism after the Christchurch attacks, which revived painful memories of the 2011 Breivik mass killings in Norway.

"It's obviously very sad. It recalls painful memories of our own experience with July 22, the most difficult moment in the post-war period in Norway."

Sweden’s Foreign Minister Margot Wallstrom tweeted that she was “shocked by the attack in Christchurch”, saying “we condemn terrorism in all forms.”

Danish Foreign Minister Anders Samuelsen also commented that “extremism has again shown its ugly face”.