Krenz was convicted of being responsible for a shoot-to-kill policy employed by border guards against people trying to flee East Germany.

Nearly 1,000 people were killed trying to escape to the West after the Berlin Wall went up in 1961.

Krenz, 62, was ordered to report to Berlin's Hakenfelde prison after the German Constitutional Court refused to hear his appeal.

As he arrived at the low-security prison in a taxi, a handful of supporters shouted: "Egon, we're with you."

The former party leader told reporters outside the jail: "I am starting my sentence, not as a criminal, but as a victim of political persecution."

Specimen charges

Krenz was convicted in August 1997 on four specimen charges relating to the shoot-to-kill policy at the Berlin Wall.

He was sentenced to six-and-a-half years but remained out of prison during his appeal process.

The constitutional court refused to hear the case after an earlier appeal had failed to overturn the conviction

The appeal hearing last year rejected his argument that he could not be convicted in the united Germany because he had been living at the time under the laws of East Germany.

Krenz told the appeal he had been unable to influence the shoot-to-kill policy because East Germany had been a satellite of the former Soviet Union.

Afterwards, he dismissed his treatment by the judicial system of the Federal Republic as "victor's justice".

He was originally sentenced with two other leading members of the ruling East German party, Guenter Schabowski and Guenther Kleiber.

Schabowski has already begun serving his three-year sentence, while Kleiber, also sentenced to three years, has been granted a delay because of his wife's ill-health.

Short reign

Krenz succeeded his mentor Erich Honecker as head of state and Communist Party leader in 1989. He had been a member of the National Defence Council that was responsible for border policy.

In an attempt to bolster the regime in the face of mass protests, he decided to open the wall on 9 November.

He was ousted by the party a few weeks later. East Germany joined West Germany the following year.