A jury in the US state of Texas has found a white police officer guilty of the murder of a 15-year-old African-American boy.

Roy Oliver had fired five bullets into a car full of teenagers last year, killing Jordan Edwards, while responding to a call of underage drinking at a party in a Dallas suburb.

The boy, who was unarmed, and four others were leaving the party after hearing gunfire, which had come from a nearby location.

Oliver fired a rifle into the car, hitting the teenager in the head.

The jury also found the officer, who was reportedly fired from his job, not guilty of two aggravated assault charges.

He could face between five and 99 years in prison for the murder conviction.

The jury had deliberated for two days before returning the rare conviction of a police officer in a high-profile shooting.

Police originally said Oliver opened fire because the car was backing up aggressively toward him.

But the department changed its account after viewing bodycam footage, saying the car was driving away when Jordan Edwards was shot.

During the trial, Oliver testified that he fired because the car was being driven toward his partner.

"I had to make a decision," he testified. "This car is about to hit my partner, there are threats inside the car, and when lethal force is being presented toward us, I had no other option but to use lethal force."

But Oliver's partner Tyler Gross testified that he had not felt in danger, according to US media reports.

"I just wanted them to stop," he said, according to WFAA TV. "I was not in fear at that point."

The Dallas County Sheriff's Office said in a statement announcing Oliver's arrest warrant last year that evidence suggested the police officer "intended to cause serious bodily injury."

The shooting was among a growing list of similar cases in which African-Americans were killed by white police officers.

The high-profile incidents, often accompanied by official or eyewitness video footage, have fuelled outrage across the United States and given rise to the Black Lives Matter movement.

Oliver is the first on-duty Texas officer in more than 40 years to be convicted in a shooting death, according to the Fort Worth Star-Telegram.