Muslim sports stars Mohamed Salah and Enes Kantar headline the list of athletes sending their thoughts and prayers to the victims of the Christchurch terrorist attack.
Forty-nine people were killed in separate attacks at the Deans Ave and Linwood Ave mosques in Christchurch on Friday afternoon.
Forty-two people are being treated for their injuries, two of them in critical condition.
Four people were arrested on Friday but one has since been released, believed to have been attempting to assist police with their own firearm.
The news has gone global, with New Zealand Prime Minister Jacinda Ardern calling it "one of New Zealand's darkest days".
Liverpool's Salah said the news was "dreadful".
"Dreadful news coming out of New Zealand this morning. My condolences go out to the families of those innocent victims who lost their lives in this act of pure evil," Salah tweeted.
Kanter, known to most New Zealanders as Steven Adams' 'Stache Brother', shared similar thoughts.
"Devastated to hear about the violence in #NewZealand," he said.
"My thoughts and prayers are with the families and friends of all impacted by this senseless act. #Christchurch. This act of violence is incomprehensible."
Adams himself tweeted with praying emojis.
Indian cricket captain, who was in New Zealand last month, was shaken by the news.
"Shocking and tragic. My heart goes out to the ones affected by this cowardly act at Christchurch.
"Thoughts with the Bangladesh team as well, stay safe."
Many New Zealand athletes based overseas woke up to the tragic news.
All Whites captain Chris Wood said he's heartbroken.
"Horrible what has happened back home in NZ. Truly heartbreaking. My love goes out to all that are affected," he said.
Former All Blacks and Wales player Shane Howarth said it was "a very sad day".
"To the Muslim community, I can only say sorry and that you are welcome in my country."
Former Chiefs and current Ireland rugby midfielder Bundee Aki also shared his thoughts.
"My prayers goes out to all the families, friends affected by this tragic news."
The news rocked the entire Irish rugby team who have a number of New Zealanders involved, including coach Joe Schmidt and his assistant Greg Feek.
I think waking up this morning to that news, it's just really tragic," said Irish captain Rory Best.
"Our heartfelt sympathies go out to all the families and anyone in that greater Christchurch area and anyone with family over there.
"Obviously we have Joe, Greg Feek, Bundee has family in New Zealand, Ronan O'Gara, good friend of a lot of the squad, he's over there as well, it's just one of that tragedies that's really hard to put into words
"You feel very helpless, all you can do is pass on your deepest sympathies, and it is really tragic.
"Definitely it was the talk of the team room this morning at breakfast, everyone was shocked and saddened by it."
Many international sports teams, including Manchester United, the Brooklyn Nets, along with multiple international rugby unions, also sent their sympathies.