US President Barack Obama says there is no clear evidence that the shooter in the massacre in Orlando, Florida, was directed externally by a larger terrorist network.

“It appears that the shooter was inspired by various extremist information that was disseminated over the internet,” the president said.

Obama said administration officials were examining various internet sites.

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The shooter, Omar Mateen, expressed allegiance to the radical group Islamic State, also known as ISIL and ISIS, in a call to the city’s 911 emergency telephone number during a standoff with police while holding hostages in a nightclub called Pulse early on Sunday.

Obama also said the United States had to think about the risks of firearms laws that allow easy access to powerful guns.

Police have said the gunman with an assault-rifle-type weapon and a handgun that were purchased legally.

Meanwhile, Republican presidential nominee Donald Trump reiterated his call for a temporary ban on Muslims entering the country in the wake of the massacre, but said it could be lifted once they were properly screened.

In a speech in Manchester, New Hampshire, that was intended to focus on Hillary Clinton, Mr Trump turned his focus to President Barack Obama and the threat of Islamic extremism through immigration.

“We must find out what is going on,” he said.

“We need to tell the truth about how radical Islam is coming to our shores.”

Mr Trump then continued to suggest the Orlando massacre was the product of immigration from Afghanistan.

“The killer, whose name I will not use or ever say, was born to Afghan parents who immigrated to the United States,” he said, adding that Mateen’s father had formerly published support for the Taliban.

“Immigration from Afghanistan into the United States has increased nearly five-fold in just one year. If we want to remain a free and open society, then we have to control our borders.”

Mr Mateen — a New York-born Florida resident and US citizen who was the son of Afghan immigrants — was shot and killed by police early on Sunday morning after a three-hour siege, in which 49 people were killed.