Munich - Two minority young men went on trial Monday over an assault in a Munich station on an elderly man which triggered calls in Germany for delinquents to be sent to boot camps.

A Turkish citizen, who has since turned 21, and a Greek national, who has since turned 18, are accused of attempted murder.

The victim, a retired school principal, 76, said he told the young men off for smoking inside a non-smoking underground station.

In a scene filmed by closed-circuit security cameras on December 20, 2007 and repeatedly broadcast on German television throughout the Christmas holiday period, the assailants knocked him to the ground and kicked him. He was critically injured, but recovered.

Both accused appeared in a Munich young person's court, because one defendant was under 18 at the time of the alleged crime. He faces a maximum term of 10 years' jail. The older accused faces a maximum sentence of life if the court treats him as an adult.

The assault in Bavaria was seized on by Roland Koch, premier of the neighbouring state of Hesse, who was running for re-election, to suggest that violence worsened if the courts were too reluctant to jail teen youths for minor violence.

Koch and other centre-right figures called for special youth jails, or boot camps, with a focus on arduous exercise and military- style discipline. Chancellor Angela Merkel voiced support for brief custodial sentences as a deterrent to juveniles.

The issue did not save Koch, whose vote share declined. He now rules Hesse at the head of a minority government.

"Soft" sentences such as probation or weekend public service are not expected at the Munich trial because of the extreme violence.

Three experts including a psychiatrist who counsels troubled youth are to testify about why the men became violent.

The accused, who live in Munich and grew up in Germany, were caught three days later, reportedly with the help of a mobile phone which they had stolen from another youth just before the attack.

Race was an unspoken issue in the debate, with immigrants seen as a threat. Throughout January, the German news media highlighted violence by minority youths, but the controversy has since calmed. (dpa)