(Releads with release of suspects, adds detail)
By Christine Soukenka
PASSAU, Germany, Dec 15 (Reuters) - German police are investigating in the neo-Nazi scene over the stabbing of a German police chief, prosecutors said on Monday, adding that two suspects detained on Sunday would be released.
Alois Mannichl, 52, police chief in the southern city of Passau, was seriously wounded when he was stabbed in front of his home on Saturday. Police said the attacker made threats with language used by far-right supporters.
Prosecutor Helmut Wachl told reporters police had detained two suspects on Sunday who fitted Mannichl's description of his assailant but said they would be released due to lack of evidence.
The stabbing of Mannichl, who had taken a firm stand against far-right supporters in recent years, shocked many in Germany.
Bavarian Interior Minister Joachim Herrmann said that if confirmed as an extremist attack, it would mark an escalation of violence not seen in the right-wing scene in decades.
Germany's police trade union said Mannichl had stood atop a "black list" of right-wingers in his region.
"This cowardly and furtive attack...shows that the far-right extremist scene does not shy away from killing people who're getting in their way," the GdP union said in a statement.
Politicians from across the political spectrum condemned the attack, with some calling for tougher sanctions on neo-Nazi crime and others saying Germany should reconsider a ban on the far-right National Democratic Party (NPD).
Right-wing parties including the NPD, which Germany's Office for the Protection of the Constitution describes as racist and anti-Semitic, have made gains in local elections, particularly in regions with high unemployment.
SHIFT TO VIOLENCE
Germany's top policeman said in August German neo-Nazis appeared to have made a tactical shift and were increasingly turning to violence.
Media said Mannichl's attacker had rung his victim's doorbell and told him: "Greetings from the national resistance, you left-wing police pig. You're not going to trample on our comrades' graves any more."
He then rammed a knife into his body, reports said.
A few months ago, Mannichl had ordered the arrest of several neo-Nazis after individuals tried to place a flag with a swastika onto the coffin of a far-right activist at his funeral, media have reported.
Although Nazi symbols, such as swastikas, are banned in Germany, parties like the NPD can get public funding because they are legitimate political parties.
(Writing by Kerstin Gehmlich; editing by Ralph Boulton)