Gunshots have been heard near a police transportation vehicle by the site of the Republican National Convention, police sources say. No injuries were reported.
An official at the law enforcement command centre overseeing security for the event had no immediate comment on Tuesday (local time).
It was not the first report of gunfire in Cleveland, which is hosting the event where Republicans are expected to name New York real estate developer Donald Trump as their candidate to face likely Democratic opponent and former Secretary of State Hillary Clinton in the November 8 election.
"In a dense urban area you get reports of things like that happening," Cleveland Police Chief Calvin Williams told reporters at a briefing Tuesday morning (local time) before the most recent report of gunshots.