Berlin (CNN) A German former nurse on Tuesday admitted murdering 100 patients, making him one of the country's deadliest post-war serial killers.

Niels Hoegel, 41, confessed to killing his patients -- between the ages of 34 and 96 -- at two hospitals in northern Germany between 2000 and 2005.

Hoegel is accused of giving his victims various non-prescribed drugs, in an attempt to show off his resuscitation skills to colleagues and fight off boredom.

On the first day of his trial at a court in Oldenburg, northwest Germany, Hoegel said the murder allegations against him were correct.

Around 126 relatives of the victims are co-plaintiffs in the trial, which is expected to run until May next year, a court spokeswoman told CNN.

Read More