US Vice-President Kamala Harris has gone on the offensive against Donald Trump in the first rally of her White House campaign, portraying November’s election as a choice between a former prosecutor and a convicted felon.

Speaking to a crowd of about 3,000 in the battleground state of Wisconsin, Harris likened her Republican opponent to fraudsters she said she had prosecuted.

Harris highlighted her experience as California's attorney general.

"I took on perpetrators of all kinds,” she said. “Predators who abused women. Fraudsters who ripped off consumers. Cheaters who broke the rules for their own gain.”

"So hear me when I say I know Donald Trump's type," Harris added. "In this campaign, I promise you, I will proudly put my record against his any day of the week.

In response, the crowd shouted "Kamala! Kamala!"

Some observers noted that the audience's enthusiasm contrasted with that seen at Biden events this electoral cycle.

When her Republican opponent's name was mentioned, many attendees chanted "lock him up", echoing a similar refrain at Trump events when he was running against Hillary Clinton in 2016.

Trump, meanwhile, assailed her record on the border, and posted on social media: “Lyin’ Kamala Harris destroys everything she touches!”

It comes a day after she secured the support of a majority of Democratic delegates, paving the way for her to become the party's nominee.

On Sunday afternoon, President Joe Biden announced he was withdrawing from the race and endorsed his vice-president amid mounting pressure from top Democrats and donors following his disastrous debate against Trump in late June.

The fledgling Harris campaign raised a staggering $100m plus (£77m) in the 36 hours after Biden’s exit.