Media playback is unsupported on your device Media caption Jim Van Horn, Pulse nightclub customer: "He (Omar Mateen) was a homosexual and he was trying to pick up men"

The man behind the worst mass shooting in recent US history was a visitor to the Orlando gay club where he carried out the massacre, witnesses say.

Chris Callen, a performer at Pulse in Orlando, Florida, told the New York Daily News that Omar Mateen had visited the venue several times.

Investigators are pursuing the reports, according to US media.

Mateen opened fire in the packed club early on Sunday, leaving 49 people dead and dozens wounded.

Police shot the 29-year-old dead after he barricaded himself in a bathroom, taking several people hostage.

"I've seen him a couple of times at Pulse, a couple of other people that I've spoken with, including an-ex security guard, have actually witnessed this guy at Pulse many times before," said Chris Callen.

In one incident, Mr Callen said Mateen had pulled a knife on a friend after being angered by a religious joke. But Mr Callen also characterised Mateen as a "nice guy", adding: "Maybe he got radicalised and hated who he was?"

Ty Smith told the Orlando Sentinel: "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."

Another man, Kevin West, told the Washington Post he he had known Mateen through the dating app Jack'd and had recognised him as he walked into Pulse in the early hours of Sunday.

"I remember details," said Mr West. "I never forget a face."

While there has been no official comment from the authorities on the claims, CNN and NBC said investigators were examining them.

'Saved by a hug'

Image copyright Reuters Image caption Mateen sprayed crowds with bullets at the Pulse club, before being shot dead himself

A man who survived the shooting has been explaining how he saved a barman's life - by hugging him.

Clubber Joshua McGill saw Rodney Sumter bleeding from multiple gunshot injuries.

He used his shirt to stem wounds to Mr Sumter's arms before being instructed by police to lie beneath him and squeeze him tight to staunch another wound in his back.

"I can hear the police officers in the front seat saying, 'Keep him conscious, talk to him'," he recalled. "That's when I learned his name."

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Jeh Johnson, the Director of Homeland Security, said on Tuesday that the shooting highlighted the need for "meaningful, responsible" gun control measures.

Mr Johnson said such controls were a public safety issue and would not infringe on the rights of responsible gun owners.

"This has become a matter of homeland security," he told CBS News. "We need to do something. We need to minimize the opportunities for terrorists to get a gun in this country."

Mateen pledged allegiance to so-called Islamic State (IS) shortly before the attack, US authorities say.

FBI Director James Comey said there were "strong indications of radicalisation and of potential inspiration by foreign terrorist organisations".

Media playback is unsupported on your device Media caption Footage from one of the victim's phones has been released by her brother

President Obama said the inquiry was being treated as a terrorist investigation, but added there was no clear evidence that Omar Mateen was directed by IS.

He will travel to Orlando on Thursday to pay his respects to the victims.

The two likely main challengers to replace him as US leader, Republican Donald Trump and Democrat Hillary Clinton, have offered differing views on how to prevent such attacks recurring.

Mr Trump proposed suspending immigration from countries with links to militant attacks targeting the US or its allies.

But Mrs Clinton warned against "anti-Muslim rhetoric", calling for better background checks on weapons sales.

The US gun deaths you haven't heard about

Media playback is unsupported on your device Media caption BBC Pop Up helped Florida residents create a video message to the global gay community

Vigils have meanwhile been held in Orlando and around the world for the victims of the attacks.

The youngest was 18, the oldest 50.

Among those killed were a couple, Juan Ramon Guerrero, 22, and Christopher "Drew" Leinonen, 32, who will have a joint funeral service, their families told Time.

Media playback is unsupported on your device Media caption Thousands of people gathered in central Orlando on Monday night, holding candles and flowers in tribute to the victims

Image copyright AFP Image caption International landmarks also paid tribute to the Orlando victims

Thousands of people gathered in central Orlando on Monday night, holding candles and flowers in tribute.

Imam Muhammad Musri, of the Islamic Society of Central Florida, said the attack had been "an act of terror, an act of hate".

"We condemn the ideology of hate and death and destruction and we call for all Muslim leaders and communities across this nation and across the world to stand up and to deal with this cancer and to remove it once and for all," he said.

Were you at Pulse nightclub or in the area at the time of the shooting? Did you know Omar Mateen? Please get in touch by emailing haveyoursay@bbc.co.uk.

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