US President Barack Obama has described Sunday morning’s gun attack on a gay nightclub in Orlando, Florida, as “an act of terror and an act of hate”.
Americans were united in “grief, outrage and resolve to defend our people”, he said.
Omar Mateen, 29, killed 50 people and wounded 53 at the Pulse club before being shot dead by police.
The so-called Islamic State group has said it was behind the attack, but the extent of its involvement is not clear.
A statement on its affiliated Amaq news agency said that an IS “fighter” was responsible.
NBC News reported that Mateen had called the emergency services before the attack and swore allegiance to IS.
The attack is the worst mass shooting in recent US history.
The gunman was killed in an exchange of fire with 11 police officers, after taking hostages at the club.
Eight of the victims have so far been named: Edward Sotomayor Jr, Stanley Almodovar III, Luis Omar Ocasio-Capo, Juan Ramon Guerrero, Eric Ivan Ortiz-Rivera, Peter O Gonzalez-Cruz, Luis S Vielma and Kimberly Morris.
A moment of silence was observed across the US at 18:00 local time (22:00 GMT).
In an apparently unrelated event, a heavily armed man was held on weapons and explosive materials charges in southern California after saying he wanted to go to a gay pride event in Los Angeles.
Mr Obama said the “brutal murder of dozens of innocent people” was a further reminder of how easy it was to acquire a deadly weapon in the US and shoot people.
“We have to decide if that’s the kind of country we want to be,” said the president, who has campaigned for stricter gun laws. “To actively do nothing is a decision as well.”
He added that it was a heartbreaking day for the LGBT community, and that an attack on any American was an attack on all.
Mr Obama has ordered flags on federal buildings to be flown at half mast until sunset on Thursday.
Later the White House said Mr Obama had postponed a joint appearance with the Democratic Party’s presumptive nominee for president, Hillary Clinton.
Mrs Clinton said in a statement: “This reminds us once more that weapons of war have no place on our streets.”
And in a message to LGBT (lesbian, gay, bisexual and transgender) people, she said: “We will keep fighting for your right to live freely, openly and without fear. Hate has absolutely no place in America.”
Meanwhile her Republican rival, Donald Trump, said Mr Obama should step down for refusing to use the words “radical Islam” when condemning the attack.
“If we do not get tough and smart real fast, we are not going to have a country anymore,” he said.
The head of the Council on American-Islamic Relations urged politicians not to “score points” or “exploit fear” in the aftermath of the attack.
In a direct message to IS, Nihad Awad said: “You do not speak for us. You do not represent us. You are an aberration.”
Mateen, a US citizen of Afghan descent who was born in New York and lived in Florida, was not on a terrorism watch list.
However, officials revealed that the FBI had twice interviewed him in 2013-14 after he made “inflammatory remarks” to a colleague, before closing their investigation.
It has emerged that he legally purchased several guns in the past few days.
Mateen worked for a private security company. His employers, G4S, said he had worked for them for nine years and carried a gun as part of his job.
In a statement, the company said he had undergone screening twice, in 2007 and 2013, and the checks had not revealed anything of concern.
His ex-wife has told the Washington Post newspaper that he was “not stable”, had a violent temper and beat her up regularly during their short-lived marriage for trivial things like not doing laundry.
The death toll means that the Orlando attack surpasses the 2007 massacre at Virginia Tech, which left 32 people dead.
States of emergency have been declared in the city of Orlando and surrounding Orange County.
- BBC
