The police said on Twitter that the only arrests had been inside the rally, but no figures were provided. A spokesman for the Police Department was not immediately available.

The raucous scene outside the convention center was matched by Mr. Trump’s fiery tone inside the rally, which protesters disrupted less than three minutes after he started speaking.

Talking for over an hour, Mr. Trump, the presumptive Republican nominee, reprised his attacks on Senator Elizabeth Warren, Democrat of Massachusetts and a fierce critic of his. He also dismissed the news media as “dishonest slime” and responded to attacks by Hillary Clinton that accused Mr. Trump of saying before the Great Recession that he wanted the housing market to collapse so that he could make money.

Calling Mrs. Clinton a “lowlife” for an online ad she put out, he said: “I’m a businessman — that’s what I’m supposed to do. That’s what I’m supposed to do.”