Muslims urged to give blood in wake of worst mass shooting in US history

American Muslims have been urged to donate blood in the wake of the worst massing shooting in the country’s history.

The call from Muslim leaders in Florida comes after a heavily armed gunman opened fire and seized hostages at a gay club in Orlando early Sunday, killing 50 people.

The attacker, who died during a shootout with police, has been named by American television networks as Afghan-American Omar Mateen from Port St Lucie in Florida.

CBS News quoted law enforcement sources, saying police are investigating whether he had ties to “Islamic extremism”. Police have not officially identified the gunman.

CNN and NBC cited law enforcement sources as saying that Mateen made a 911 phone call shortly before the shooting pledging allegiance to the Islamic State group.

But the suspect's father told NBC news his son may have been motivated by homophobia and not by his Muslim faith.

In the wake of the attack, a senior FBI official told Reuters that that there were suggestions that the gunman might have had leanings toward Islamic State militants but that this required further investigation.

"Do we consider this an act of terrorism? Absolutely, we are investigating this from all parties’ perspective as an act of terrorism," said Danny Banks, special agent in charge of the Florida Department of Law Enforcement. "Whether that is domestic terrorist activity or an international one, that is something we will certainly get to the bottom of."

When asked if the FBI suspected the gunman might have had inclinations toward "militant Islam," including possible sympathy with Islamic State, Ronald Hopper, an assistant FBI agent in charge, told reporters: "We do have suggestions that the individual may have leanings toward that particular ideology. But right now we can’t say definitively."

In the wake of the shooting, the Florida chapter of the Council on American-Islamic Relations (CAIR-FL) called on Muslim Americans to donate blood in the city and joined with interfaith leaders to condemn the deadly shooting spree.

"We condemn this monstrous attack and offer our heartfelt condolences to the families and loved ones of all those killed or injured. The Muslim community joins our fellow Americans in repudiating anyone or any group that would claim to justify or excuse such an appalling act of violence,” said CAIR-Florida's Orlando regional coordinator Rasha Mubarak.

Members of the American Muslim Community Centers in Orlando also expressed their shock and sadness at the “senseless killings”.

A spokesperson for the group said: "AMCC and its members offer their deepest condolences to those affected by this tragedy and we stand with our fellow Americans in this difficult time.

"Ramadan is a month of deep reflection and prayer. Senseless violence has no place in our religion or in our society. We strongly condemn this heinous act of violence against humanity". Ramadan, the Muslim fasting month, runs this year from 6 June to 5 July.

The chaotic events unfolded over a three-hour period, beginning at around 2 am (0600 GMT) when shots rang out amid the throbbing music at the Pulse Orlando nightclub near closing time.

Police said the shots were fired by a gunman armed with an assault rifle and a handgun.

A police officer working "extra duties" at the club responded, joined by two other officers, who engaged the suspect in a gun battle.

The suspect then went back inside the club and took hostages. Police then stormed the venue, using explosives and breaking through a wall with a wheeled armored vehicle known as a BearCat, killing the suspect in a blaze of gunfire, according to the police account.

The White House later said that President Barack Obama has been briefed by his homeland security and counterterrorism aide on the mass shooting.

Obama asked to receive regular updates on the unfolding investigation, and instructed the federal government to provide any assistance necessary, a statement said.

It was unclear whether all the victims were killed by the gunman or if some died in the ensuing shootout with police.

Speaking earlier to Sky News, clubber Ricardo Negron, who was inside when the shooting began, described how the gunman raked the club with bullets.

"People just dropped on the floor. I guess the shooter was shooting at the ceiling because you could see all the glass from the lamps falling," he told the network.

He described hearing "non-stop firing" which probably lasted less than a minute but felt like a lot longer.

"There was a brief pause in the shooting and some of us just got up and ran out the back.

"People have definitely been injured - or worse."

Emergency vehicles swarmed the area, with at least one crisis command vehicle at the scene.

The Pulse club advertises itself online as "Orlando's hottest gay bar". On its Facebook page, the club warned patrons: "Everyone get out Pulse and keep running."

Witness Christopher Hanson said he heard "loud banging noises, like gunshots going off".

"I didn't see any of the actual shooters. I just saw bodies going down and I was ordering a drink at the bar.

"I fell down. I crawled out. People were trying to escape out the back. I just know that when I hit the ground I was crawling and I hit my elbows and my knees," he told CNN.

He said there was "blood everywhere".

Rosie Feba was at the club with a friend when the shooting broke out.

"She told me someone was shooting. Everyone was getting on the floor," Feba told the Orlando Sentinel. "I told her I didn't think it was real, I thought it was just part of the music, until I saw fire coming out of his gun."

Earlier, terrified survivors - who moments before were laughing and dancing with friends - described how the gunman sprayed the club with bullets, prompting a police SWAT team to storm the venue.