He urged President Donald Trump to stop “encouraging fools” of her after a person was killed during clashes between rival groups.
Biden said: “I condemn violence in all its forms by anyone, whether from the left or the right … and I challenge Donald Trump to do the same … We must not become a country at war with itself.”
“What does President Trump think will happen when he continues to insist on fueling the flames of hatred and division in our society and uses intimidation policies to incite his supporters? He frantically encourages violence.”
Republicans deny Trump is seeking to stoke violence, say he wants to restore law and order, and accuse mayors and governors of Democratic states of losing control of cities ravaged by demonstrations and which have seen violence, arson and looting.
Jason Miller, a senior Trump campaign adviser, said on Twitter that Biden had “remained idle for months, refusing to condemn violence and chaos by his allies in cities ruled by Democrats.”
Demonstrations against racism and police brutality have engulfed the United States since the killing of 46-year-old George Floyd, after a Minneapolis policeman kneeled on the neck for about nine minutes in May.
Downtown Portland has seen protests every night for nearly three months after Floyd’s death, and police there said they made several arrests after a person was shot dead on Saturday night.