Italy is to deploy troops to Iraq to defend a strategic dam from the Islamic State (Isis) group, the government has announced. Prime Minister Matteo Renzi said the 450-strong military contingent will secure the Mosul dam on the Tigris River, providing protection for an Italian firm that has secured a contract to repair it.

Built in the 1980s, the facility is a key source of water and energy for the nearby city of Mosul, which is under Daesh (IS) control. The dam, Iraq's largest, also fell into the hands of the jihadi group last year but was seized back by Kurdish militias supported by US airstrikes in August 2014.

"[It] is at the heart of a very dangerous zone, on the border with IS. It is seriously damaged if it were to collapse the whole of Baghdad would be destroyed," Renzi said on national television.

When IS conquered the site fears were raised it would blow it up to unleash a massive tidal wave that could have caused severe flooding from Mosul all the way down to Baghdad, which lays 400km to the south.

After the Islamists were ousted, Italian construction group Trevi secured a $2bn (£1.3bn) contract to fix the facility, but security conditions have since been too frail for works to start.

"The contract [to repair it] has been awarded to an Italian company and we will send 450 of our men there to help fix it alongside the Americans," Renzi said.

The new troops will add to the 750 that Rome already has on the ground in Iraq. The deployment close to the frontline, however, represents a significant step-up of Italy's involvement in the conflict as existing forces are tasked mainly with training and air reconnaissance duties.