Rising tensions after the deadly ambush of police officers in Dallas and subsequent protests nationwide have led Cleveland and Philadelphia to adjust security plans for the national political conventions this month.

Cleveland, where the Republican National Convention is to begin Monday, has moved up by a week the activation of a tip line for reporting suspicious activity, Police Chief Calvin Williams said. Security plans have been "ramped up" because of the Dallas shootings last week, which killed five officers and wounded nine others at the end of a march to protest the fatal shooting of black men by police in Louisiana and Minnesota, he said.

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

There have been no credible reports of threats against officers in Cleveland or the surrounding region, Williams said. But adding to concerns over security is Ohio's status as an "open carry" state, meaning it's legal to carry a gun in the open without a permit. One supporter of the presumptive Republican presidential nominee, Donald Trump, has already asked Cleveland march participants to be mindful of the message that openly carrying might convey.

"We really don't want people to bring long guns," said Tim Selaty Sr., lead organizer for Citizens for Trump.

In Philadelphia, where the Democratic convention begins July 25, Police Commissioner Richard Ross said Monday that his agency won't change its general approach for policing protesters at the Democratic convention. He said the Dallas shootings have "required that we do things different tactically," although, like Cleveland's police chief, he declined to elaborate on specific strategies.

With Philadelphia police already on heightened alert because of Dallas, an incident at a downtown high-rise hotel late Monday rang alarm bells. Two people were found on the rooftop with smoke bombs and camera equipment and taken into custody. There was no immediate word on what they were doing.

One Philadelphia group's police protests grew hostile in recent days, with anti-police chants and at least one speaker praising the Dallas gunman. That group, the Philly Coalition for REAL Justice, has sought a permit for a march in downtown Philadelphia on the second day of the convention. It's pending.

But a lack of official permission to demonstrate will not stop them or anyone else from protesting; police say the lack of a permit alone will not result in arrests.

The U.S. Secret Service, which is in charge of security planning for both conventions, didn't return a message Monday seeking comment.

Even before Dallas, Cleveland's convention raised concerns about the potential for violent clashes between Trump supporters and opponents. And on Monday, Trump predicted more violence.

"I mean, you were having big, big trouble in many cities," he said. "And I think that might be just the beginning for this summer."

The convention will be a test for police in Cleveland, which last year began operating under a reform-minded agreement called a consent decree after a U.S. Justice Department investigation concluded officers had shown a pattern of using excessive force and violating people's civil rights.

Cleveland and Cuyahoga County plan to have hundreds of jail cells available to house arrested protesters. Police and the FBI also interviewed several protesters over the past month to ask about their protest plans.

At least one group has already canceled a Cleveland march following the Dallas shootings.

"In the current uncertain environment nationwide, we are concerned for police officers who would be charged with protecting our marchers and advocates as well as for the safety and well-being of our march participants," Michael Weinstein and Tracy Jones, with the AIDS Healthcare Foundation, said in a statement. The group still plans a rally on the campus of Cleveland State University Sunday.

Philadelphia's police approach includes having on-scene leadership at every level to "remind men and women in uniform to remain patient, professional and maintain their resolve," Ross, the police commissioner, said.

"This is not an easy to thing to do when people are an inch away from your nose calling you the most vile, despicable things you've ever heard," Ross said. "We have to be flexible, and willing to adapt. We will allow people to protest and exercise their First Amendment right."