New York (AFP) - Philadelphia was put under a curfew on Friday for the second time this week and National Guard troops were deployed in the US city after days of unrest following the police killing of a Black man.
The city, the largest in the state of Pennsylvania, has seen looting, protests and clashes with police since Monday's fatal shooting of 27-year-old Walter Wallace, which was captured on video posted to social media.
The US has seen a wave of protests and rioting since the police killing of George Floyd in May in Minnesota, when an officer was filmed pressing his knee to handcuffed Floyd's neck until he went limp.
Philadelphia's citywide curfew will be in effect from 9 pm to 6 am, the city posted on Twitter.
"During this time, people may leave their homes only to go to work, seek medical or emergency assistance, or drop off a mail-in ballot," it said.
Mayor Jim Kenney said on Twitter that the National Guard troops will be sent to "critical government buildings or other infrastructure and may be sent to other key areas like commercial corridors".
The mayor, a Democrat, stressed that their deployment was not linked to the November 3 election.
The curfew was reinstituted with the city expecting more protests this weekend.
A curfew had been in effect on Wednesday night, but was lifted on Thursday.
Police shot Wallace, who was carrying a knife, after he refused to drop the weapon as his mother tried to restrain him.
A lawyer for Wallace's family, Shaka Johnson, said he was bipolar and the call to emergency services was for an ambulance.
The two officers, whose names have not been released, have been suspended and an investigation is ongoing.
The family has viewed body-camera footage from the officers and say it shows Wallace "in obvious mental health crisis".
Kenney said he had agreed with the Wallace family and authorities that the footage and audio from the emergency call would be released on November 4 -- a day after the presidential election -- "in the hope that it will provide enough time to ease tensions".
Wallace's death and the subsequent demonstrations and unrest have reignited a political clash between Republicans and Democrats days before the election.
Pennsylvania is a key battleground state in the race between President Donald Trump, who has focused on the unrest to bolster his claims to be the "law-and-order" candidate, and his Democratic challenger Joe Biden.