By Ayman al-Warfalli, Ahmed Elumami and Nayera AbdallahTRIPOLI, Aug 11 (Reuters) - Renewed violence in the strategic Libyan city of Zawiya has once again disrupted the oil industry in the OPEC member country, with state oil firm NOC saying it could declare force majeure if drone attacks on energy assets in the city continued.

A drone hit a naphtha tank at Libya's Zawiya refinery on August 8, causing a contained leak. NOC Chairman Suleman confirmed no fire or injuries.

The incident came two days after a drone crashed into an untreated naphtha tank at the Zawiya refinery early on Saturday, causing a leak that staff managed to control.