BERLIN: German police have detained two suspects in connection with the murder of a pro-immigration politician shot by a far-right sympathiser, who has confessed to the crime, the Federal Prosecutor's Office said on Thursday.

The prosecutors said one of the men, identified as Elmar J, had sold the gun Stephen E used to shoot Walter Luebcke, who was found lying outside his home in the state of Hesse on June 2. Privacy laws prohibit publishing their family names.

The second suspect, Markus H, is believed to have been a middleman who introduced Stephen E to the gun dealer.

The two suspects were detained in Kassel, where Luebcke was murdered, and Hoexter, a town about 70 km farther north. Their apartments were searched, the prosecutors said, giving no details.

Luebcke's killing has revived a debate about whether Germany was doing enough to combat far-right groups, after the chance discovery in 2011 of a neo-Nazi cell, the National Socialist Underground (NSU), whose members murdered eight Turks, a Greek man and a German policewoman from 2000 to 2007.

Interior Minister Horst Seehofer said on Wednesday that the investigation of Luebcke's murder would continue, even though Stephan E confessed to the crime and told investigators he had acted alone.

Seehofer also said security services would get more staff and resources to monitor far-right groups, especially on the Internet.

MINUTE'S SILENCE

Stephan E's DNA matched forensic samples collected on the terrace where Luebcke, who headed the regional government in the city of Kassel, was found dead.

Luebcke was a hate figure on far-right internet forums critical of Chancellor Angela Merkel's 2015 decision to welcome around a million refugees at the height of the refugee crisis.

The 2011 discovery of the NSU unleashed fierce criticism of the intelligence agencies and police for underestimating the risk of far-right violence. Reforms were then introduced, such as closer coordination between agencies and regions.

The BfV, Germany's domestic intelligence agency, will present its annual report on Thursday, which should shed light on political extremism.

Merkel's Christian Democrats, of which Luebcke was a member, have said the far-right Alternative for Germany (AfD) must share blame for the Luebcke murder, by legitimising a language of hate that encourages political violence.

The AfD has rejected suggestions that its anti-immigration stance was to blame for Luebcke's death and said its members were the victims of left-wing violence.

On Wednesday, a regional AfD lawmaker in the Bavarian parliament was condemned after he remained seated as the chamber stood for a minute's silence to remember Luebcke.