Matteo Renzi has been sworn in as Italy's youngest premier, heading a new government he says will swiftly tackle old problems.

ITALY-POLITICS/

Newly appointed Italian Prime Minister Matteo Renzi, right, rings a silver bell to signify the start of his first cabinet meeting, next to his predecessor Enrico Letta, at Chigi Palace in Rome. (Tony Gentile/Reuters)

Chief challenge for the broad coalition that took office on Saturday is a feeble economy that has only just begun showing tentative signs of rebounding after several years of stagnation.

The Democratic Party leader also vowed to cure Italy's chronic political instability with electoral reforms aimed at making the country more governable.

The centre-left former Florence mayor, 39, chose many newcomers for his decidedly young-looking cabinet. In a first, there are as many women ministers as men.

One of his non-political appointees, Economy Minister Pier Carlo Padoan, missed the swearing-in. The Organization of Economic Cooperation and Development's chief economist was attending a meeting in Australia when tapped on Friday.