American officials are increasing security for the upcoming Republican and Democratic political conventions. This comes after five police officers were shot and killed in Dallas.

FBI Director James Comey recently spoke at a congressional hearing about the possibility of domestic terrorism.

He said "anytime there's a national spotlight on a political event in the United States, there's a risk that groups that aspire ... to engage in acts of domestic terrorism will be attracted."

Jeh Johnson is head of the Department of Homeland Security. He told lawmakers he is concerned about the possibility of violence. And he is concerned about demonstrations at the conventions "getting out of hand."

Johnson said he will travel to Cleveland and Philadelphia to personally inspect the security at both conventions.

About 50,000 people are expected at the Republican National Convention in Cleveland, Ohio from July 18 to July 21. Donald Trump is likely to be named the party's presidential candidate.

A week later, from July 25 to July 28, about the same number of Democrats will meet in Philadelphia, Pennsylvania. They will gather to formally name Hillary Clinton as the Democratic presidential candidate.

Cleveland Security

In Cleveland, security concerns are complicated by the fact Ohio is a so-called "open carry" state. That means that anyone with a legal permit to carry a gun can do so openly.

"We're going to make sure we stay vigilant," said Cleveland Police Chief Calvin Williams. "But we also want to make sure that we ask the community to remain vigilant."

Williams said he will "uphold the law in the state," but he would prefer that people not openly carry guns during the convention. He said the city is prepared for the event.

The U.S. Secret Service banned guns inside the main convention site, and in the security area around it. But people with firearms will be able to carry them in areas that surround the convention site, as long as they are holstered.

Cleveland officials have been concerned about the possibility of violent clashes between people who support Trump, and his opponents. In the protest areas, guns will be permitted, but common items like glass bottles, large backpacks, mace and canned goods will be banned from the event area.

Philadelphia Security

Philadelphia Police Commissioner Richard Ross said that the Dallas shooting had "required that we do things different tactically." But he did not say what those plans would be.

Philadelphia is handling protesters differently than Cleveland. The city will permit supporters of Clinton's opponent, Bernie Sanders, to gather in a park across from the convention building. There is also a new border, 1.5 meters high, to protect the convention at the Wells Fargo Center.

A spokeswoman for the Philadelphia mayor told VOA that city officials expect demonstrations outside the center to be peaceful.

"(We) ... feel confident that we're prepared for demonstrations and any public safety threats," she said.

However, there is another issue that could create problems for people in Philadelphia. The city's airport workers have voted to go on strike during the convention.

Dan Bulla is president of the Treadstone Group, a private security firm in Charlotte, North Carolina.

He told VOA that law enforcement officials are preparing for physical acts of civil disobedience, like blocking streets. But they are also preparing for "extraordinary crimes" such as terror and cyber-attacks. Bulla has been involved in helping with security planning for the conventions.

Wayne Lee wrote this story for VOA news. Anne Ball adapted it for Learning English. Hai Do was the editor.