A US federal court has ordered a new sentencing hearing for an ex-Black Panther activist on death row for the 1981 killing of a white policeman.

A Philadelphia appeals court said Mumia Abu-Jamal, 57, must have a hearing within six months.

He has been on death row since 1983 after his conviction in the killing of Philadelphia Officer Daniel Faulkner.

He has maintained his innocence, and death penalty opponents across the world have rallied around his case.

On Tuesday, the Third District Court of Appeals upheld its 2008 ruling that the death penalty instructions given to the jury at Abu-Jamal's 1982 trial were unclear, but it declined to overturn Abu-Jamal's conviction.

The appeals court had been ordered by the US Supreme Court to review the case....