At least seven people, including a 14-year-old girl, have been killed and dozens more injured in three separate mass shootings in Philadelphia, Tennessee and Phoenix between Saturday night and early Sunday morning, said officials.
The latest spate of gunfire came as US officials, including President Joe Biden, and campaigners continue to call on Congress to crack down on gun violence in the wake of recent deadly mass shootings in a supermarket in Buffalo, New York and a primary school in Uvalde, Texas.
At least three people were killed and 12 others injured after multiple shooters opened fire into a "large crowd" in a popular entertainment district in Philadelphia.
Police officers were patrolling the bustling downtown area of South Street - where hundreds were said to be in the area - when they heard multiple gunshots shortly after 11.30pm on Saturday.
Officers headed towards the sound of the shooting and saw several suspects firing into a large crowd just before midnight, said police.
They found several civilians "suffering from gunshot wounds, lying on the pavement and in the street," said Philadelphia Police Commissioner Danielle M. Outlaw.
An officer shot at one of the suspects from about 30 feet away, but it was unclear if the suspect was hit. He dropped his gun and fled the scene, said authorities.
No arrests have yet been made.
Among the victims were two men and a woman, whose names were not immediately made public by authorities.
The conditions of those who were wounded by gunfire remained unknown.
"Yesterday was a dark day for Philadelphia," said Ms Outlaw at a press briefing on Sunday.
"While many of us were out enjoying the beautiful day in the city, a horrendous and unthinkable act happened in a very popular local and tourist hangout - acts that claimed the lives of three people, we now know, and injured 12 others."
A 14-year-old girl was killed and eight others were wounded early on Saturday in a shooting amid a crowd of people at a strip mall in downtown Phoenix.
"Many rounds were shot into this crowd of people as everyone fled the area" at 1am in downtown Phoenix, said Sergeant Andy Williams.
The 14-year-old girl died after being taken to hospital, two women have life-threatening injuries, and six have injuries that are not life-threatening.
Mr Williams said the wounded range in age from about 17 to 24. No suspects have yet been identified.
The shooting happened about an hour after police reported that a teenage boy was shot and killed outside his home about three blocks away. It was not immediately clear if the two shootings were related.
Phoenix Mayor Kate Gallego responded to the shooting on Twitter, saying: “Seems we can’t go a day without another mass shooting.”
“Time has run out,” she said. “Change must happen now.”
A shooting near a Tennessee nightclub early on Sunday morning led to three deaths and 14 people suffering gunshot wounds and other injuries, police said.
Officers responded to a report of a shooting at 2.42 am and found multiple victims upon arrival.
Fourteen people were hit by gunfire and three were hit by vehicles while trying to flee the scene, according to Chattanooga Police Chief Celeste Murphy.
Two people died from gunshot wounds and one person died after being hit by a vehicle.
Sixteen of the victims were adults and one was a juvenile and several remained in critical condition, she said.
Want a quick and expert briefing on the biggest news stories? Listen to our latest podcasts to find out What You Need To Know
There were multiple shooters and Murphy asked anyone in the community with information about the shooting to come forward. She said police believe it was an isolated incident and authorities don't believe there's an ongoing public safety threat.
Chattanooga Mayor Tim Kelly, who described himself as an “avid hunter” and gun owner, called on Congress to enact “common sense regulations” to address gun violence. Kelly is an independent.
“That doesn’t mean taking guns away from responsible gun owners, but it does mean mandatory background checks and prohibiting high-capacity magazines that allow shooters to hurt dozens of people without even having to reload,” he said at a press conference.
He added: “It’s going to be a long summer, and we have got to get out in front of it and put a stop to it."