The official says the attack took place early today and targeted the Mellitah Oil and Gas complex near Zwara, about 110 kilometres from the capital, Tripoli. The complex is a joint venture between Libya's National Oil Corp. And Italy's largest energy company, Eni SpA. The militiamen fled the site briefly after seizing weapons and equipment from the guards.
The official spoke on condition of anonymity because he was not authorised to brief reporters.
A military official told Libya's official news agency that military helicopters are searching for the attackers.