An Oklahoma police officer has been found guilty of a series of sex attacks against black women while on patrol. Daniel Holtzclaw, 29, burst into tears in court after he was found guilty of five counts of rape and 13 counts of sexual assault against eight women while working in one of the state's poorest areas.

Among his victims were a 17-year-old girl he raped after driving her home when he saw her walking alone, and a grandmother in her 50s who he attacked after pulling her over and telling her to get into his patrol vehicle to question if she had been drinking.

In many of the cases, the police officer targeted victims who were sex workers, drug users or had criminal records, coercing them into sexual acts by promising to drop any drug charges or ignoring any outstanding warrants and not report the sexual assault and rapes against them.

One victim told the court during the trial: "I didn't think anyone would believe me. I'm a black female," reported the Oklahoman. His 17-year-old victim added: "What am I going to do? Call the cops? He was a cop."

Holtzclaw now faces spending the rest of his life in prison after a jury recommended he is sentenced to at least 263 years for his crimes. Following the guilty verdict, Oklahoma County district attorney David Prater said: "Justice was done today, and a criminal wearing a uniform is going to prison now."

The case comes as US police are under increasing scrutiny for a series of high-profile racially charged incidents. Many have expressed their frustration that it has not attracted the same media attention as the shooting of Ferguson teenager Michael Brown by officer Darren Wilson or the chokehold death of Eric Garner by New York police officer Daniel Pantaleo.

However, supporters of the victims who did attend the court during the trial were there to sing happy birthday to the officer following the guilty verdict to Holtzclaw, who had turned 29 on 10 December. Holtzclaw was cleared of a further 18 charges he faced during the trial, including rape, sexual battery and stalking. He is due to be sentenced in January.

The lead detective in the case, Kim Davis, said after the verdict: "I feel horrible for his family. It's brutal, but I think justice was served," The Associated Press reported.

The Oklahoma City Police Department said in a statement they were "pleased" with the jury's decision. The force added: "It was a long and difficult trial and deliberation process for all involved. It is obvious the jury took their responsibilities very seriously and considered every piece of evidence presented to them. We are proud of our detectives and prosecutors for a job well done. To the jury, we thank you for your service. We are satisfied with the jury's decision and firmly believe justice was served."