The call comes after a witness was assassinated on the steps of a prison in Lima as he was about to testify.

He was to give evidence in the case against Fernando Zevallos, who is now on a US blacklist of the world's most wanted drug traffickers.

The latest killing marks the growing boldness of drugs gangs operating in Peru as cocaine production increases.

On Wednesday afternoon, the former drugs trafficker was entering a prison complex in Lima to testify in a case involving a drugs baron, when he was shot twice in the back of the head.

The killer fled the scene jumping onto a motorbike driven by another man.

Police described it as a trademark drugs killing, the latest in a string of murders of cartel members, officials, and even a judge dating back two years.

Anxious defendants

In this case the witness, known by the alias of Shevaco, was a former drugs assassin.

He was due to testify in the case against Fernando Zevallos, the former owner of what was Peru's largest carrier, Aero Continente.

Mr Zevallos himself does not feel immune from danger.

Both he and his co-defendant have called for more security.

Meanwhile, on Friday, Justice Minister Rosario Fernandez called for more protection for the prosecutors and judges in the case.

Experts say drug traffickers in Peru are using more brutal tactics, increasingly using hitmen to eliminate their rivals, as is common in countries such as Colombia and Mexico.

Peru is the world's second largest producer of cocaine and its production has grown sharply in recent years, despite various campaigns against it.

Experts warn that if the authorities don't take steps to slow down the growing of coca and the processing of cocaine in the interior of the country, the influence of Colombian and Mexican drugs cartels will grow and with it the death threats and assassinations.