Former US Vice President and Democratic presidential nominee Joe Biden on Monday issued a stinging rebuke to President Donald Trump's accusations that the former condones violence that has erupted in US cities. "The simple truth is Donald Trump failed to protect America. So now he's trying to scare America," Biden said in remarks at Carnegie Mellon University in Pittsburgh. Biden called Trump power hungry and lambasted the president for what Biden sees as a lack of moral leadership — a common refrain from the former vice president on the campaign trail. "We are facing multiple crises — crises that, under Donald Trump, keep multiplying," Biden said. "COVID, economic devastation, unwarranted police violence, emboldened white nationalists, a reckoning on race, declining faith in a bright American future. The common thread? An incumbent president who makes things worse, not better. An incumbent president who sows chaos rather than providing order." The Democrat's comments came amid sharp tensions between the rival candidates over unrest in US cities. Trump has made "law and order" a major theme of his campaign. The two candidates have in recent days been trading insults over clashes in Portland, Oregon. A man linked to a right-wing group was shot dead there on Saturday, as elsewhere in the city a pro-Trump rally clashed with Black Lives Matter protesters. Condemning violence and rioting reported in many parts of the country, Biden said: "Rioting is not protesting. Looting is not protesting. Setting fires is not protesting. None of this is protesting, it's lawlessness, plain and simple," said Biden. "And those who do it should be prosecuted. Violence will not bring change. It will only bring destruction. It's wrong in every way." Doubling down on his attack on Trump, the former vice president said that the president "long ago forfeited any moral leadership in this country". "He can't stop the violence — because for years he has fomented it," Biden said, adding: "We need justice in America. And we need safety in America. We are facing multiple crises — crises that, under Donald Trump, keep multiplying." "Does anyone believe there will be less violence in America if Donald Trump is re-elected?" he asked. — Agencies