"We will continue to support the government of the new democratic Libya, which we are sure will spare no effort in preventing Libya's new course from  being hijacked," Monti said at a press conference in Rome.

"We condemn with maximum firmness this brutal act," he said, expressing condolences to the US government and the families of the victims.

Libya is a former Italian colony and Italy is one of the top foreign investors in the country as well as being one of its top trade partners.

Italy also played a crucial role in the conflict to oust Libyan dictator Moamer Kadhafi last year, acting as a base for NATO air raids.

An armed mob outraged over a low-budget movie mocking Islam stormed the US consulate in Benghazi late on Tuesday, firing rocket-propelled grenades into the compound before looting it and torching the building.

Foreign Minister Giulio Terzi said the attack had provoked "horror and disdain" and called for "light to be shed on it as soon as possible".