President Obama said Monday there is no clear evidence that the gunman in this weekend's massacre at a gay nightclub in Orlando, Fla., was directed by a foreign terror group or part of a larger plot.

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Speaking to reporters in the Oval Office, Obama said the attack appears to be a case of “homegrown extremism.”

The president said the shooter, Omar Mateen, was “inspired by various extremist information that was disseminated over the internet.”

“At this stage, we see no clear evidence that he was directed externally,” Obama said.

Obama spoke after receiving a briefing on the attack from his top law enforcement officials and national security advisers, including FBI Director James Comey and Homeland Security Secretary Jeh Johnson.

Forty-nine people were killed and 53 injured early Sunday morning when Mateen opened fire inside the Pulse nightclub in the central Florida city.

The deadliest mass shooting in U.S. history prompted renewed fears about the federal government’s ability to prevent attacks by lone-wolf assailants.

The FBI interviewed Mateen, a 29-year-old U.S. citizen, three times in 2013 and 2014 after he made threatening statements to co-workers, claimed ties to terror groups and reportedly made contact with an American suicide bomber.

But the agency closed the investigation when investigators were unable to verify his comments or ties to extremists.

Obama said the FBI has done a “proper job” but added that preventing attacks by individuals inspired online is “one of the biggest challenges we are going to have.”

Top Republicans have suggested the problem starts with Obama.

Presumptive GOP presidential nominee Donald Trump Donald John TrumpUS reimposes UN sanctions on Iran amid increasing tensions Jeff Flake: Republicans 'should hold the same position' on SCOTUS vacancy as 2016 Trump supporters chant 'Fill that seat' at North Carolina rally MORE has questioned Obama’s willingness to fight Islamic extremist groups.

He’s sparked controversy by calling on the president to resign if he doesn’t vocally acknowledge “radical Islam” as a threat to the United States. And the businessman even suggested Monday that Obama has intentionally buried his head in the sand on the topic.

Obama did not respond to Trump’s comments, instead focusing on the need to counter violent extremism online and make it harder for individuals inspired by the Islamic State in Iraq and Syria to obtain firearms.

"We are also going to have to make sure that we think about the risks we are willing to take about being so lax in how we make very powerful firearms available to people in this country," Obama said.

He said the raging debate about terrorism and gun control is not an "either/or" proposition.

Obama said it is “crazy” that individuals on terror watch lists are allowed to purchase firearms, adding that law enforcement officers are slow to be alerted or not alerted at all when they do.

“It’s a problem,” he said. “And we have to do some soul searching.”

Updated at 12:07 p.m.