The Italian government on Saturday defended its decision to use soldiers to patrol cities in an effort to curb crime, rejecting criticism that it will "militarise" the streets.

"There is a strong call from citizens for better control of the streets, for improved safety," Defence Minister Ignazio La Russa told Sky Italia television.

"My hope is that particularly in the evening, in the cities, these troops can ensure greater safety."

The government announced on Friday that up to 2,500 soldiers, some of whom have served in Afghanistan and Kosovo, would be made available for a trial period of six months to bolster the police in difficult urban areas.

Silvio Berlusconi's new conservative government won an April election on a law-and-order ticket, and crime and public safety have stayed on top of the political agenda since Berlusconi took office.

The government's decision was attacked by the centre-left opposition, with Roberta Pinotti, defence spokesman for the Democratic party, expressing "firm opposition to the militarisation of the streets".

Italy's main trade unions said rather than using soldiers the government should make better use of 25,000 police who are doing desk work, and the mayor of Turin said the move was "populist demagoguery" that would hurt tourism and Italy's image abroad.

"I have only seen soldiers on the streets in Bogota, but there the situation is rather different," Sergio Chiamparino told La Repubblica daily.

La Russa said he did not understand the criticism but specified that the use of soldiers would not be permanent, with the initial six-month period being renewable "just once."

"Very often just seeing a (soldier's) uniform can be sufficient as prevention. I don't see what the problem is," he said.