US President Barack Obama has said all Americans should be concerned about the frequent police killings of black men.
His comments, as he arrived in Poland for a Nato summit, came after two more black men died in such incidents.
Philando Castile was shot dead during a traffic stop in Minnesota on Wednesday, while Alton Sterling was shot dead by police in Louisiana a day before.
On Thursday night, protests were held across the US over the police use of lethal force against African Americans.
Demonstrations took place in several cities including, Dallas, New York, Chicago, Washington and the two cities that features in the latest incidents, Baton Rouge in Louisiana and St Paul in Minnesota.
Shots were fired at the protest in Dallas, local media report, with two police officers reported injured by gun fire.