The killing of at least 49 people at two mosques in Christchurch was a "heinous crime of religious hatred", the UAE's Prime Minister has said.
Sheikh Mohammed bin Rashid, also Vice President and Ruler of Dubai, said the attacks came on the traditional day of peace for Muslims, as they gathered for Friday prayers.
"On behalf of myself and my country, which devoted a whole year for tolerance, we offer our condolences to New Zealand, the victims' families and all Muslims," he wrote in Arabic on Twitter.
"We condemn the crime and express our deepest sorrow. We call the world to reassess their stand in order to establish interfaith tolerance."
Sheikh Mohammed was among the Muslim world leaders to condemn the atrocity, which also left at least 20 more victims seriously injured, some critically.
Sheikh Mohamed bin Zayed, Crown Prince of Abu Dhabi and Deputy Supreme Commander of the Armed Forces, said the world must "fight hatred" together.
"Our deepest condolences to the families of the victims of the hate crime that took the lives of innocent Muslims performing Friday prayers in New Zealand," he wrote on Twitter.
"We call on the world to fight hatred."
Imran Khan, Pakistan's prime minister, also expressed his condolences and said he was alarmed by the further rise of Islamophobia.
"Shocked and strongly condemn the Christchurch, New Zealand, terrorist attack on mosques," he wrote on Twitter.
"This reaffirms what we have always maintained: that terrorism does not have a religion. Prayers go to the victims and their families.
"I blame these increasing terror attacks on the current Islamophobia post-9/11 where Islam & 1.3 bn Muslims have collectively been blamed for any act of terror by a Muslim. This has been done deliberately to also demonise legitimate Muslim political struggles."
King Abdullah II of Jordan spoke of a "heinous massacre against Muslims praying in peace" and "an appalling terrorist crime".
"It unites us against extremism, hatred and terrorism, which knows no religion," he said.
"May the victims’ souls rest in peace."
US president Donald Trump said that his "warmest sympathy and best wishes goes out to the people of New Zealand after the horrible massacre in the mosques,".
"The US stands by New Zealand for anything we can do. God bless all!"
In a statement, Al Azhar University, Egypt's 1,000-year-old seat of Sunni Islamic learning, said the attacks had "violated the sanctity of the houses of God".
"We warn the attack is a dangerous indicator of the dire consequences of escalating hate speech, xenophobia, and the spread of Islamophobia."
Britain's Queen Elizabeth said she was "deeply saddened by the appalling events in Christchurch today".
"Prince Philip and I send our condolences to the families and friends of those who have lost their lives", she wrote on Twitter.
"I also pay tribute to the emergency services and volunteers who are providing support to those who have been injured. At this tragic time, my thoughts and prayers are with all New Zealanders."
The Queen was joined in her condolences by British Prime Minister Theresa May.
In a video posted to YouTube, she said: "Through terror attacks that have taken place on UK soil we know only too well the pain that such horrifying attacks can cause. As New Zealand has stood by us so we stand shoulder to shoulder with them, and with Muslims in New Zealand, here in the UK and around the world.
"There can be no place in our societies for the vile ideology that drives and incites hatred and fear. Together we will defeat those who seek to destroy our values, our way of life and seek to divide us," she added.
Mevlut Cavusoglu, Turkey's foreign minister, also said the attack was a deliberate demonising of Muslim political struggles.
"Not only the perpetrators, but also politicians and media that fuel the already escalated Islamophobia and hate in the West, are equally responsible for this heinous attack," he wrote on Twitter.
Norwegian Prime Minister Erna Solberg said the attack sparked memories of the 2011 massacre of 77 people by extremist Anders Breivik at a left-wing youth gathering on a Norwegian island and with a bomb in Oslo.
"It shows that extremism is nurtured and that it lives in many places," she said.
Bangladeshi Foreign Minister Shahriar Alam said it was "extremely lucky" the country's cricket team did not suffer casualties. The team, in the city to play a match against the New Zealand national team, arrived for Friday prayers as the shooting occurred.
"I can't even imagine what would have happened if they were there five minutes earlier," he said on social media.
Law enforcement agencies in New Zealand are continuing the investing into the killings and the main suspect behind the killings, who has been named as Brenton Tarrant.