ALGIERS: Al-Qaida's North Africa arm has claimed responsibility for a mortar attack on a gas plant in the Sahara jointly operated by Britain's BP and Norway's Statoil, calling it a protest over shale gas extraction. No one was injured in the attack Friday and Algerian troops fanned out to hunt the perpetrators. The Defence Ministry said two homemade rocket shells fell near the Krechba production site near In Salah, which is overseen by Algerian state company Sonatrach. Al-Qaida in the Islamic Maghreb issued messages saying it targeted the site because the government suppressed protests over environmental fallout from shale gas extraction there. The messages, published Saturday by the SITE extremist monitoring group, also threatened Western companies — specifically those extracting shale gas — and the Algerian government. The attack recalled a deadly hostage-taking at another Algerian gas plant in 2013, which left 37 dead. Algeria-based AQIM, which also claimed that attack, drew a direct link between the two. AQIM also said it contacted BP and Statoil hours before Friday's incident to allow them to evacuate staff. Statoil spokesman Knut Rostad told The Associated Press on Saturday he would not comment on that claim. 'After the attack the companies involved are doing an assessment of what happened and find out if anything needs to be done. I have no further comments,' he said. Statoil said its staff was safe and. BP said there were no reports of injuries to its employees. While the attacked inflicted no damage, it was a reminder of the vulnerability of even heavily guarded oil and gas fields. AQIM also claimed responsibility for an attack Sunday on a beach resort in Ivory Coast that killed at least 18 people.