Carjacker kills three children in US

Two men have been charged with murder and sexual assault in connection with a carjacking that killed three children and left their mother fighting for her life in the US city of Philadelphia.

Jonathan Rosa, 19, and Cornelius Crawford, 24, were also charged on Monday with robbery, kidnapping, conspiracy and related offences - including sexually assaulting the woman they allegedly carjacked on Friday morning.

Rosa and Crawford were taken into custody on Sunday night, concluding a citywide manhunt launched on Friday morning after a carjacked Toyota 4Runner lurched out of control and into a family selling fruit at Allegheny and Germantown avenues.

The crash killed 15-year-old Keiearra Williams, 10-year-old Thomas Joseph Reed, and seven-year-old Terrence Williams. Their mother, Keisha Williams, was critically injured and remained on Monday night at Temple University Hospital. Williams announced that former NBA great Charles Barkley has offered to pay for the children's funerals.

Another woman who had been selling fruit with Williams and her family, Thelma Brown, 69, suffered a broken ankle and a bruised sternum, and remained on Monday at Hahnemann University Hospital.

Also injured was a 45-year-old real estate agent who was carjacked, and then forced to perform oral sex on both men after they forced their way into her car.

According to a police report, the two took $US3000 ($A3245) from the woman, who suffered broken ribs, cuts and bruises in the subsequent crash. She was also taken to Temple, where she remained on Monday in stable conditions.

Veteran detectives, some assigned to the unit for 15 years, said it was one of the saddest cases they had ever seen.

He thanked the public for tips and video footage that poured in as news of the crash spread on Friday. He said several witnesses had given police detailed descriptions of Rosa and Crawford, and identified them once they were in custody.

Ramsey said one of the first witnesses on the scene - a man who helped pull the real estate agent out of the battered 4Runner - had found a mobilephone inside the car and initially mistaken it for his own, an identical model.

Once home, Ramsey said, the man realised that the phone was not his and called 911. Police traced the phone to Rosa and took him to the Homicide Unit for questioning on Saturday afternoon.

Rosa denied any involvement with the crash, Ramsey said, and told police he had misplaced his phone. Without enough evidence at the time to hold him, Ramsey said, he was released.

Rosa surrendered to police on Sunday, accompanied by his mother and pastor.

Crawford was apprehended by US Marshals and homicide detectives on Sunday night.