Berlin - An African-born man claiming to have a German family background was on a hunger strike Monday after a bitter 17-year struggle to gain citizenship in Germany.

Gerson Liebl, 46, was detained by police on Thursday - pending possible deportation to Togo, the West African state where he was born.

At the weekend, his Togolese wife, Ginette, 43, and eight-year-old son Gergi were also picked up by the police after visiting him in the detention centre in Gruenau on Berlin's eastern outskirts. The family is now being held together at the detention centre.

Reached by phone Sunday, Liebl told the Deutsche Presse-Agentur dpa that he and his wife were on hunger strike in protest at the police action. "It's illegal what they have done," he said.

"I've done nothing wrong," he said, his voice choking.

"I'll fight the authorities all the way if their intention is to kick me and my family out of the country," he said, adding that his son had been due to start school in Berlin on Monday.

The thought that he and his family could be sent back to Togo after so many years shocks him.

"I'm of German descent," he insists. "I'm battling for the abolishment of racist colonial laws which are still valid today in Togo," he says.

The story surrounding Liebl's claim to German citizenship dates back to the late 19th and early 20th centuries when Togo was a German protectorate.

A specialist in tropical diseases at a hospital in the Togo capital Lome, Liebl's late grandfather, German-born Friedrich Karl Georg Liebl, fell in love with Kokoe Edith Ajavon, the attractive daughter of a local chieftain.

The couple had a son, Johann Baptist Liebl, and were wed at a traditional African-style tribal ceremony in Togo - but not as German legal experts later said in a church or registry office.

Mixed marriages were banned under then German imperial law, and Johann was duly registered as a mulatto (a person with a white and a black parent).

Karl Liebl returned home to the Bavarian town of Straubing in 1911, leaving his African bride and son behind. Subsequently he married a German woman by whom he had three children.

Friedrich Karl Georg Liebl's grandson Gerson Liebl was born in 1962. He was a son of Johann Baptist Liebl.

Bright at school, Gerson learned German and got a job as a goldsmith before flying to Frankfurt in 1991 to seek asylum, and later German citizenship.

It was also when his long struggle with the German bureaucracy began in earnest.

Officials argued that Gerson's father, Johann Liebl, had never possessed German citizenship, nor did he qualify for it under colonial law. Ordered to leave the country, Gerson Liebl refused to comply.

Police raided his apartment and during a scuffle Liebl claimed he suffered injuries. Later he was given a nine-months suspended sentence for allegedly resisting his arrest.

It then emerged the police had acted without an arrest warrant and the sentence against him was quashed.

Eventually, he and his family were allowed to remain in Germany, and he moved to Straubing in Bavaria, where his grandfather had once lived.

But in 2005 his residence permit ran out, and was not extended, due to a technicality. He was also out of work.

Liebl raised his grievances with a German parliamentary committee set up to deal with foreigners' grievances.

In Straubing, town hall officials speak of Liebl's extraordinary tenacity in his legal battles. Rows of files relating to his case line office walls.

Martin Panten, the head of Straubing's foreigners' affairs office, says that in the 13 years he's been working there he has never known a case like Liebl's. "He contests everything," said Panten.

On three occasions Liebl has taken his case to German's highest court, the Federal Constitutional Court. "That's most unusual," Panten told the German newspaper, Berliner Zeitung.

While there is a degree of sympathy for Liebl's difficulties, Straubing officials say there is nothing they can do to help him. "We cannot change the nation's laws. Only the Bundestag (the German parliament) can do that," he says.

But in March this year Bavaria's highest administrative court rejected Liebl's latest bid to remain in the country and be given German nationality.

His 17-year-tussle with German officialdom appeared to have come to a sad end. (dpa)