Image copyright Getty Images Image caption The former nurse pictured in court in November 2014

A former German nurse has admitted killing 30 patients in the hospital where he worked, a court was told.

The 38-year-old allegedly confessed to taking the lives of the patients by injecting them with an overdose of heart medication.

He made the confession to a psychiatric expert who relayed the evidence in court.

Investigators said his motive was to improve his own resuscitation skills.

The former nurse has been on trial since September and is accused of murder and attempted murder.

He is alleged to have killed three patients and tried to kill two others at a clinic in Delmenhorst, near Bremen in north Germany.

But a psychiatric examiner told the court in nearby Oldenburg that he had confessed to as many as 30 killings.

The patients are believed to have been injected with heart medication between 2003 and 2005.

In a further 60 cases he injected patients but managed to revive them, according to the psychiatric assessor.

Police are investigating more than 100 suspicious deaths at the Delmenhorst clinic.

The nurse, identified by the authorities only as Niels H, had already been sentenced to seven-and-a-half years in prison in 2008 for attempted murder.