As New Zealand reels from the horrific terrorist attack that has left at least 49 people dead and 48 people injured, celebrities around the world have shared their sentiments and reactions to the shocking tragedy.

The massacre took place as Muslims gathered for Friday afternoon prayer, while suspected killer Brenton Tarrant opened fire in both Al Noor Mosque in Christchurch city’s centre and Masjid mosque in the suburb of Linwood.

He was heavily armed and fitted two improvised explosive devices to his vehicle, which the military later diffused.

Two other people have been arrested, described as the terrorist’s “associates”, while a third who was earlier apprehended is not connected to the attacks.

New Zealand-born Oscar winner Russell Crowe was one of the first celebrities to tweet, joining his countrymen in mourning after the shootings occurred at two mosques.

The Gladiator star, who spent his youth in Wellington, ended his tweet with the Maori expression "Kia Kaha," meaning "stay strong."

Terminator star and former governor of California Arnold Schwarznegger expressed his condolences and support to the victims, saying “the world stands with you”.

Actors Alyssa Milano, Nia Vardalos and Debra Messing also shared their sadness of the attack with their followers.

Avengers star Mark Ruffalo added his sympathies while singer John Legend urged his followers to unite against “this white supremacist terrorist movement.”

CEO of Apple, Tim Cook, shared a Martin Luther King quote along with his sentiments that he is “devastated” by the shocking massacre.

Artist Cat Stevens, also known as Yusuf Islam, posted a poignant picture of a dove holding a silver fern, a symbol of New Zealand, while Star Trek actor George Takei expressed that “hate knows no boundaries”.

Colin Hanks, son of prolific actor Tom Hanks, also added his apologies.

The alledged killer will face court in Christchurch this morning.