WASHINGTON — Presidential hopeful Kamala Harris had strong words for her opponent Donald Trump during a rally in northwestern Pennsylvania on Monday.

Harris said Trump's behavior was becoming increasingly "unstable and unhinged" after the former US President made comments suggesting that the US military could be used to deal with the "enemy from within."

"He considers anyone who doesn’t support him or who will not bend to his will an enemy of our country,” Harris said, adding that she thought a second term with Trump in power would be dangerous for America.

The two candidates spoke as they campaigned for the hotly contested state of Pennsylvania.

The rally marked Harris' 10th visit to the state this campaign season alone, as Trump gave a speech in a town hall in suburban Philadelphia after traveling to two other towns in the state.

Trump made his comments during a Fox News interview on Monday in response to a question about "outside agitators" potentially disrupting election day.

“I think the bigger problem is the enemy from within,” Trump said. He added: “We have some very bad people. We have some sick people, radical left lunatics. And I think they’re the big — and it should be very easily handled by, if necessary, by National Guard, or if really necessary, by the military, because they can’t let that happen.”

Both sides believe the race for Pennsylvania, where Joe Biden beat Trump by about 80,000 votes four years ago, could be close.

In a town hall in suburban Oaks on Monday Trump spoke about his desire to increase US oil drilling, which he linked to driving down costs.

“We’re going to drill baby drill, we’re going to have so much energy and we’re going to bring prices down,” Trump said.

He also claimed government data was being manipulated in order to aid the Democrat campaign.

Meanwhile, Harris encouraged US citizens to vote early in the state where 7 million are expected to vote in the upcoming election.

Pennsylvania and its 19 electoral votes, the most of any swing state, have generated the most attention by far from the Democratic and Republican presidential campaigns.

Michigan, with 33 visits, and Wisconsin, with 29, are the next most-visited states, illustrating how both campaigns are focusing on winning states that had been part of the Democrats’ so-called “blue wall” until Trump emerged as the Republican standard-bearer. — Euronews