No evidence Orlando attack was directed from abroad

President Barack Obama said on Monday there was no evidence that the massacre of 49 people in a Florida nightclub was directed from abroad or was part of a larger plot.

After being briefed by his top security aides, Obama said "we don't yet know" the shooter's motivations.

The President said 29-year-old Omar Mateen did appear to have been "inspired by various extremist information that was disseminated over the Internet," however he added "at this stage we see no clear evidence that he was directed externally."

"It does appear that at the last minute he announced allegiance to ISIL, but there is no evidence so far that he was in fact directed by them," he said, using an acronym for the Islamic State group.

"There's also no direct evidence that he was part of a larger plot."

IS earlier claimed responsibility for the massacre, saying in a radio bulletin that it was carried out by "one of the soldiers of the caliphate."

Obama's comments were echoed by FBI chief James Comey, who added that his agency is "highly confident" Mateen was "radicalised" by online propaganda.

Another avenue of investigation is the gunman's homophobia, as his father has told US media outlets that the shooter was disgusted by seeing gay men kissing.

"And of course, we are working to understand what role anti-gay bigotry may have played in motivating this attack," said Comey, stressing that the investigation was at an early stage.

The slaughter triggered worldwide shock and outrage, but has also raised questions about US gun laws. The suspect was allowed to legally buy an assault rifle and handgun despite raising red flags.

"There are certain common sense things that Congress could do that would make it harder for any individual to get their hands on a weapon of war," White House spokesman Josh Earnest said.

The FBI admitted it had previously investigated Mateen, the American of Afghan descent, but had cleared him of extremist ties.

Relatives and acquaintances have painted a picture of a violent and unstable young man who had beat his ex-wife and expressed homophobic views.

Agencies contributed to this report.