During congressional testimony, Homeland Security Secretary Jeh (jay) Johnson said he's concerned that demonstrations outside the convention hall may get out of hand.
He told lawmakers that roughly 4,000 US government personnel will be based in Cleveland to ensure the safety of people there.
"I am concerned about the possibility of violence," Johnson told the House Homeland Security Committee. He added that in Ohio it is legal to openly carry firearms.
FBI Director James Comey said there will be "hundreds of people" from the bureau focused on assessing intelligence related to groups that aspire to commit acts of domestic terrorism.
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"Anytime there's a national spotlight on a political event in the United States there's a risk that groups that aspire to do just that, to engage in acts of domestic terrorism, will be attracted," Comey said. "It's a threat we're watching very, very carefully."
"We have been planning and preparing for both conventions for over than a year," he said.