Italy's far-right League party is facing controversy and anger after one of its councillors was arrested over allegations he shot dead a Moroccan in a public square.

       Massimo Adriatici, a League councillor for security in the municipality of Voghera, was involved in the shooting in the northern Italian town on Tuesday night.

       The victim, a 39-year-old Moroccan man, was fatally wounded by a gunshot to the chest. Adriatici has been placed under house arrest pending an investigation into the incident.

       The leader of the far-right League party, Matteo Salvini, has defended the councillor and says the shooting was conducted in "self-defence".

       "He is a professor of criminal law, former police officer, criminal lawyer, known and esteemed in this city of Pavia, victim of an aggression to which he responded accidentally," he said in a video posted on social media.

       "He accidentally retaliated with a shot that unfortunately killed a foreign national."

       Salvini ignored calls from socialist politicians in Italy to condemn the incident and has claimed that the victim had a criminal record.

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       "Unfortunately, the foreign citizen was known in the city and to the police for his violence, aggression and even obscene acts in public places," the former interior minister said.

       "I have heard the left and the Democratic Party asking, let's wait for the reconstruction of the facts ... defence is always and in any case legitimate," he added.

       Adriatici -- a former police commander -- had reportedly called the authorities when he believed the Moroccan man was disturbing the customers at a bar and pushed him, which led to the fight.

       The politician, who was carrying a pistol, claims that a shot went off as he fell to the ground, according to ANSA news agency.

       He has now suspended himself from his post, the mayor of Voghera Paola Garlaschelli said.

       "What happened in Voghera is a huge event, which should make everyone, including the League, reflect," said Vinicio Peluffo, head of the centre-left Democratic Party in the northern Lombardy region.

       "It will be up to the judiciary to reconstruct what actually happened, but it is necessary for everyone, without exception, to condemn the idea of do-it-yourself justice," he said on Facebook.

       "Public order and ensuring compliance with the law are the responsibility of the police, certainly not of a councillor who, however you look at it, was armed in a public square."

       "If for the League, carrying a gun means safety, we are really worried. Because this habit brings blood, not peace and order."

       Like other western European Union countries, Italy has tough laws regulating the ownership and use of firearms.