Dusseldorf - German police who coached members of the Libyan security forces in their spare time may have used classified information on police training methods, prosecutors said Friday.

Some 30 police specialists, soldiers and former members of the elite police commando group GSG-9 were involved in the clandestine operation two years ago, officials said.

No active GSG-9 members took part in the training programme, which was organized through a private security firm founded by a former GSG-9 member, according to media reports.

The Defence Ministry said a sergeant serving with a crack division of mountain troops had been suspended pending an investigation that he was involved in the operation while on holiday.

Eight policemen were also under investigation in North Rhine- Westphalia, Germany's most populous state, although only one was suspected of a criminal offence.

Prosecutors said they were looking into reports that secret information relating to the state's police training methods were used by the officers who went to Libya.

"The behaviour of the policemen is completely unacceptable," said the state's interior minister, Ingo Wolf.

According to the Sueddeutsche Zeitung daily, the private security firm hired the Germans to train or organize training programmes for the Libyans during their free time.

The men were flown out to Libya and paid 15,000 euros (23,400 dollars) for their services, the report said.

A report in the newspaper Westfalen-Blatt said the Germans gave the Libyans lessons in shooting, personal security and self-defence. It said two of the officers spent six months in Libya after taking unpaid leave of absence from their jobs.

The activities took place in 2006 at a time when Libya was largely isolated because of its links to terrorism and poor human rights record.

Libyan leader Moamer Gaddafi has since guided his North African nation away from its status as a pariah state, but it is still a long way from a society based on law and justice, according to the rights organization Amnesty International.

The German police union criticized the actions of the police officers involved in the training programme, saying they harmed the reputation of the police and posed a threat to Germany's security.

German Defence Minister Franz Josef Jung said the involvement of a member of the armed forces in such activities was "not acceptable." (dpa)