US Democratic presidential candidate Joe Biden has used a speech in the battleground state of Pennsylvania to accuse President Donald Trump of being the very opposite of a "law and order" leader.

His remarks in Pittsburgh come as the two men criticized each other over violence at protests in Portland, Oregon, with Trump blaming the city's Democratic mayor for allowing the situation to escalate.

A 'toxic presence'

"Fires are burning and we have a president who fans the flames rather than fighting the flames," Biden said, describing Trump as "a toxic presence in our nation for four years."

Biden said Trump had "long ago forfeited any moral leadership" and was unable to stop the violence "because for years he has fomented it."

Biden also hit back at assertions made by Trump that he was weak on crime and ready to implement policies favored by his party's most liberal wing.

"Ask yourself: Do I look like a radical socialist with a soft spot for rioters? Really?" he asked.

Months of protests

The swing state of Pennsylvania helped propel Trump to victory in 2016. Trump and Vice President Mike Pence are both scheduled to make appearances there at campaign events later this week.

The violence in Portland erupted on Saturday night when hundreds of Trump supporters clashed with Black Lives Matter protesters. One man was shot dead in the aftermath of the clashes.

The incident occurred against the backdrop of nationwide demonstrations that have swept the country since George Floyd, a Black man, died in May after a Minneapolis police officer knelt on his neck for nearly nine minutes. New protests erupted in the state of Wisconsin last week after another Black man, Jacob Blake, was shot seven times in the back by police in front of his children, paralyzing him.

Trump has consistently called for more "law and order" as the way to properly address the protests, while claiming that the Democrats and their candidate would be soft on crime. The Democrats, in their turn, accuse Trump of exploiting the tensions to curry favor with his base.

tj/aw (Reuters, dpa)