Washington, Oct 2 (IANS): Republican presidential nominee Donald Trump has warned of voter fraud in "certain areas" and mocked Democratic rival Hillary Clintons health and marriage while suggesting she should be imprisoned.

Speaking to a crowd of nearly 5,000 in Pennsylvania on Saturday night, Trump made some of his wildest accusations yet about his opponent and the integrity of American elections, the Guardian reported.

Trump attacked his rival in starkly personal terms. He said of her "she has bad temperament, she could actually be crazy" and went on to imply that she had been unfaithful for her husband.

"I don't even think she's loyal to Bill, if you want to know the truth. And really folks, why should she be, right," Trump said.

The Republican nominee whose rallies have long included loud chants of "lock her up" directed towards Clinton, said bluntly on Saturday "she should be in prison".

Trump also warned of the specter of voter fraud without evidence, revisiting accusations he first made in August that there will be voter fraud in "certain areas" of Pennsylvania, a statement that was a clear indication about African-American areas of Philadelphia city.

"Watch your polling booths, because I hear too many stories about Pennsylvania, certain areas," the Republican nominee told the almost exclusively white crowd in Manheim.

He added "we can't lose an election because you know what I am talking about".

The Republican nominee also complained about what he saw as a rigged debate and insisted that he actually bested Hillary Clinton in Monday night's presidential debate.