Two police officers were shot and wounded outside government headquarters in Rome on Sunday, sparking chaos just as Italy's new coalition cabinet was being sworn in.

The attack occurred about a kilometre away from the presidential palace where prime minister Enrico Letta and his ministers were taking the oath of office.

Witnesses say a man in a suit and tie opened fire on the policeman at close range at the headquarters, off Rome's main shopping street.

One policeman was shot in the neck and is in a serious but not life-threatening condition, while the other was shot in the leg and was less seriously hurt.

A passerby was also injured in the attack.

The shooter, named by Italian media as unemployed man Luigi Preiti, was tackled to the ground by police and arrested at the scene.

Newly-installed interior minister Angelo Alfano says the attack was an "isolated incident".

"The tragic and criminal act this morning was carried out by an unemployed 49-year-old man who showed signs of wanting to commit suicide," he said.

But there were immediate calls for politicians to try to calm a volatile public mood exacerbated by a long slump in the euro zone's third largest economy.

"All political forces have to work together to lower the level of tension that the economic, social and institutional climate has already created," centre-left parliamentarian Emanuele Fiano said.

The attack cast a shadow over the launch of the new government, which comes after two months of bitter post-election deadlock watched closely by European partners.

Mr Letta was the first to take the oath of office at a ceremony led by president Giorgio Napolitano, who appointed him after the centre-left won February elections but without the majority needed to govern.

The 46-year-old, one of the European Union's youngest prime ministers, is expected to unveil his program in a parliamentary session on Monday, before the government is put to a confidence vote in parliament on Tuesday.

The deadlock had thwarted efforts to end the worst recession in Italy in 20 years, and Mr Letta has said he wants to move quickly to tackle unemployment - currently 11.6 per cent - and boost growth.

The leftist leader also wants to move away from the austerity imposed by his technocrat predecessor Mario Monti to protect Italy from the eurozone debt crisis - a promise which will be followed closely by investors concerned about Italy's two trillion euro debt mountain.

Unveiling his new cabinet on Saturday, Mr Letta said he was proud to have included younger ministers and more women to help renew a tired political scene and rebuild confidence in the discredited political class.

The new coalition will bring his party together with their centre-right arch rivals, the People of Freedom Party, which counts former prime minister Silvio Berlusconi as a prominent member.

The scandal-plagued ex-leader will not be in the ministry, but his close ally Angelino Alfano will serve as deputy prime minister and interior minister.

Enrico Letta (R) with Italy's president Giorgio Napolitano after announcing the new coalition government. ( AFP Photo: Vincenzo Pinto )

Reuters/AFP