ORLANDO (AFP) - United States President Barack Obama on Tuesday (June 14) voiced solidarity with the LGBT community after the shooting rampage at an Orlando gay nightclub, calling the gunman an "angry, disturbed, unstable young man who became radicalised".

After a meeting of his National Security Council, Mr Obama said the country's thoughts were with survivors and relatives of the dead, as well as the lesbian, gay, bisexual and transgender (LGBT) community "who were targeted". "You are not alone. The American people and our allies and friends all over the world stand with you," Mr Obama said.

He reiterated the official belief that gunman Omar Mateen - a practising Muslim - had absorbed extremist propaganda online, noting: "He appears to have been an angry, disturbed, unstable young man who became radicalised."

The President spoke by phone on Tuesday with French President Francois Hollande, who expressed his condolences. Both leaders reaffirmed their commitment to destroying the Islamic State in Iraq and Syria (ISIS), the White House said.

Mr Obama will travel to Orlando on Thursday.

Investigators were working to untangle the motive of Mateen, as witnesses said the 29-year-old American of Afghan descent - who was married with a child - frequented the popular nightspot and used gay dating apps.

ISIS claimed responsibility for the shooting early on Sunday. The Federal Bureau of Investigation (FBI) said Mateen pledged allegiance to the ISIS leader in 911 calls made during the killing spree - the worst mass shooting in US history.

Forty-nine people were killed and 53 wounded after Mateen opened fire at the Pulse nightclub in Orlando, a resort city in central Florida best known as the home of Walt Disney World.

MSNBC and ABC News, citing unnamed law enforcement officials, reported that Mateen's wife may have had prior knowledge of her husband's plan and could face criminal charges.

Noor Mateen, 30, was cooperating with the Federal Bureau of Investigation, and claims she tried to convince her husband not to go through with the shooting, the networks said.

An FBI spokesman declined to confirm the reports to AFP.

Security has been stepped up at Disney theme parks amid reports - based on his wife's statements to investigators - that Mateen may have scouted Disney World as a possible target.

The probe took a new turn after witnesses said Mateen - who was killed in a shoot-out with police when they stormed the venue - had been a regular at Pulse.

"Sometimes he would go over in the corner and sit and drink by himself, and other times he would get so drunk he was loud and belligerent," Mr Ty Smith told the Orlando Sentinel.

Another Pulse regular Kevin West told the Los Angeles Times that Mateen messaged him on and off for a year using a gay chat app.

Clubgoers told local media and MSNBC that Mateen had been using multiple gay apps, including the "hook up" app Grindr.

And a man who attended law enforcement training classes with Mateen in 2006 told the Palm Beach Post that the gunman had once asked him out on a date.

Mateen's former wife Sitora Yusufiy, who has said he beat her, told CNN he "confessed to me... that he very much enjoyed going to clubs and the nightlife".

"I feel like it's a side of him or a part of him that he lived but probably didn't want everybody to know about."

The authorities have identified all 49 victims, who ranged in age from 18 to 50. Of the 53 wounded, 27 remained hospitalised on Tuesday, with six in critical condition, doctors at Orlando Regional Medical Centre said.

Mr Angel Colon suffered three bullet wounds to his leg - which was shattered as people trampled him to escape Pulse - and offered a harrowing account of the carnage.

"I can hear the (gunshots) closer, and I look over and he shoots the girl next to me. And I'm just there laying down. I'm thinking, 'I'm next. I'm dead,'" Mr Colon told reporters.

"Everybody could hear him talking to 911, saying that the reason he is doing this is because he wants America to stop bombing his country," recounted another survivor, Ms Patience Carter.

She told of a chilling moment when the gunman asked if there were any African-Americans present - before telling them: "You know I don't have a problem with black people, this is about my country."

The shooting hit Orlando's Latino community hard - the club was hosting a Latin-themed party that night. Thousands joined a vigil late on Monday.

Still, the response was not all supportive. A Baptist preacher in California sparked uproar after praising the massacre as "great", saying he wasn't sad that "50 sodomites died".

"It's like the equivalent of asking me... ' Hey, are you sad that 50 paedophiles were killed today?'" pastor Roger Jimenez of the Verity Baptist Church said in his sermon just hours after the carnage.

"Um, no, I think that's great... I think Orlando, Florida, is a little safer tonight."

His comments, posted on YouTube before being taken down, were denounced by LGBT activists and local officials.

Jimenez said his remarks were taken out of context.

The slaughter has raised questions about US counter-terror strategy - the FBI said it had investigated Mateen but cleared him of extremist ties.

But a fiery Mr Obama lashed out at Republicans, especially presidential hopeful Donald Trump, for anti-Muslim rhetoric that he said was counterproductive to the fight on extremism.

"Where does this stop?" he said.

"Are we going to start treating all Muslim Americans differently? Are we going to start subjecting them to special surveillance? Are we going to start discriminating against them because of their faith?"

The rampage has also raised questions about gun laws. Mateen legally bought the assault rifle and handgun used in the attack.

Mr Obama has demanded that the Republican-controlled Congress pass legislation to curb the sale of assault-type weapons - a measure that conservatives say violates their constitutional right to bear arms.