President Trump offered his “warmest sympathy” and America's full support to the people of New Zealand following the deadly massacre allegedly carried out by a white nationalist at a mosque during prayer services Friday.

The attack left 49 dead and more than 20 injured.

“My warmest sympathy and best wishes goes out 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 U.S. stands by New Zealand for anything we can do. God bless all!” Trump tweeted Friday morning.

49 KILLED AND MORE THAN 20 SERIOUSLY INJURED IN NEW ZEALAND MASS SHOOTING TARGETING MOSQUES

The attacks at two mosques were allegedly carried out by a 28-year-old Australian-born citizen, who is in custody after claiming responsibility. The man posted a white nationalist manifesto, spanning 74 pages, immediately before the massacre, and even broadcasted a horrific live stream of the terror attack.

Australian Prime Minister Scott Morrison called the man “an extremist, right-wing, violent terrorist.” Of the other three people in custody, one of whom was a woman, officials said at least one may not be connected to the attacks.

After the attacks, New Zealand Police Commissioner Mike Bush told mosques nationwide to “close your doors until you hear from us again.”

Two improvised explosive devices were found in a vehicle after the shooting, one of which was disabled and one that police were working to defuse. It wasn’t clear if the vehicle was the same one the 28-year-old suspect was seen driving in the live-streamed video of the attacks.

NEW ZEALAND COMMUNITY RUSHES TO AID MOSQUE SHOOTING VICTIMS AMID GUNFIRE, REPORTS SAY

Officials said 41 people were killed at the Masjid Al Noor mosque in central Christchurch and seven were slain inside the Linwood Masjid Mosque, about three miles away from Masjid Al Noor. Another person died at a local hospital.

National Security Adviser John Bolton on Friday also weighed in on the attacks saying that the White House is “gravely disturbed” by the shooting massacre, saying it seemed to be a hate crime. Bolton said the U.S. is in touch with New Zealand officials to offer assistance.

“The United States strongly condemns the attack in Christchurch. Our thoughts and prayers are with the victims and their families," White House Press Secretary Sarah Sanders said Friday. "We stand in solidarity with the people of New Zealand and their government against this vicious act of hate.”

Ivanka Trump also condemned the attack, offering support to New Zealand and Muslim communities around the world.

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"49 innocent people were slaughtered in their place of worship during the terrorist attack on Christchurch Mosques. We join New Zealand and Muslim communities around the world in condemnation of this evil as we pray for the families of each victim and grieve together," she tweeted.

Fox News’ Louis Casiano, Samuel Chamberlain, and The Associated Press contributed to this report.