Passau, Germany - German police freed on Monday two men initially suspected of stabbing a police chief who has been vilified by neo-Nazis.

Alois Mannichl, 52, chief of police in the southern German city of Passau, survived the Saturday attack outside his home by a shaven- headed man who yelled neo-Nazi abuse.

Public prosecutor Helmut Walch said Monday both suspects were local men and had matched a description by Mannichl.

But hours later the men were released. Police said they had found no proof of their involvement. Joachim Herrmann, interior minister of Bavaria state, had identified the two as far rightists.

Mannichl was recovering. The knife rammed into his chest missed his heart by only 2 centimetres.

A single assailant rang the bell at Mannichl's home and attacked him when he opened the door.

Police suspect he was targeted because Passau police have kept local neo-Nazis under tight scrutiny. The rightists, who term themselves German nationalists, have alleged persecution.

Officials of Bavaria state's main party, the centre-right Christian Social Union (CSU), called for the far-right National Democratic Party (NPD) to be declared a neo-Nazi movement and banned.

Last month the NPD accused the police chief of harassing its members during a rally to "remember Germany's war dead."

In July, neo-Nazis went on the rampage in the city after the grave of a deceased functionary was opened and police removed a Nazi flag that had been draped over the coffin.

"Greetings from the national resistance, you left-wing police pig. You won't trample on the graves of our comrades any more," the 1.90- metre attacker was reported to have told Mannichl.

After stabbing him, the assailant threw away the 11-centimetre-long knife and escaped in a waiting car.

There are around 31,000 members of extreme right-wing groups in Germany, about 10,000 of whom are prepared to resort to violence, according to the domestic intelligence agency, the Office for the Protection of the Constitution.

The NDP, seen by many in Germany as a neo-Nazi organization, has legislative seats in two of the 16 German states, but no representation at federal level. (dpa)