Rome - Italy's conservative government approved Tuesday the deployment of 500 troops in a mafia-infested area near the southern city of Naples where six African immigrants were gunned down last week.

On Monday, police arrested a 29-year-old man - a convicted member of the Camorra, the Neapolitan version of the mafia - in connection with last Thursday's killings in Castel Volturno.

The attack shocked Italy and Interior Minister Roberto Maroni, speaking following a cabinet meeting on Tuesday, said the state had promptly replied to the "massacre."

"First we dispatched an extra 400 police, now we have taken the decision to deploy the troops," he said.

Maroni also welcomed the arrest of the suspect, Alfonso Cesarano, and the decision by prosecutors to add the "aggravating circumstance" of "terrorism" to his murder charge.

Cesarano, who was arrested at his parents' home and is believed to be one of a commando of Camorra hit-men, was convicted in April on Camorra-linked drug trafficking charges.

The fact that he was free to carry out the shootings because his initial jail sentence was commuted to house arrest, has provoked outrage with opposition leaders demanding Maroni explain the matter before parliament.

But the interior minister rejected the criticism saying the house arrest order had been issued by an appeals court and that the government could not interfere with Italy's independent judiciary.

"However, we are now working to ensure that people convicted of mafia association will not be granted house arrest provisions," he added.

The six Africans - three men from Ghana, two from Liberia and one from Togo - were gunned down shortly after an Italian casino owner was shot dead in a nearby town.

Investigators believe the same hit-men were responsible for both attacks, and were probably linked to a drugs turf war.

The killings triggered rioting by dozens of African immigrants in Castel Volturno who denied their victims were criminals. Ghana's ambassador to Italy travelled to Castel Volturno over the weekend to help quell tempers.

Prime Minister Silvio Berlusconi has made fighting crime a pillar of his programme and in August the government deployed 3,000 troops to assist police maintain security in the main cities.

But critics say such measures - including the introduction of harsher penalties for law-breaking immigrants - target petty crime and not the mafia's larger scale activities. (dpa)