Two bombs exploded on Thursday at the Kerdasa gas unit outside Cairo, Al-Ahram's Arabic website reported.

Once an Islamist stronghold, Kerdasa (15km from Cairo) was raided by security forces on 19 September. The district's police station had been abandoned after it was hit with rocket propelled grenades and gunfire following the violent dispersal of two Islamists sit-ins in Cairo on 14 August.

On Thursday, preliminary investigations revealed that three of the gas agency's guards were tied up by six assailants, who then left three bombs in the agency that supplies a power station and an industrial zone, Al-Ahram reported.

One bomb exploded in a control room, partially burning it. The two other bombs were left near a gas pipeline. The first one exploded, damaging part of the pipeline without causing a gas leak. The second one was later defused, Al-Ahram said.

Earlier Thursday, bomb disposal experts defused a hand-made grenade found near a hotel in the Cairo neighborhood of Mohandessin, Al-Ahram also reported.

Egypt has faced a volatile security situation since the popularly-backed military ouster of Islamist president Mohamed Morsi on 3 July.

Attacks against security forces have increased, especially in the Northern Sinai Peninsula where the army says it is waging a war against militants. Police stations have repeatedly come under attack nationwide.

On 7 September, three mortar rounds were found tied to railway tracks between the Suez Canal cities of Suez and Ismailiya. They were defused before exploding.