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 Defense Ministry said two homemade rocket shells fell near the production site near In Salah.

Al-Qaida in the Islamic Maghreb issued messages saying it targeted the site because the government suppressed protests over pollution from shale gas extraction there. The messages, published Saturday by the SITE extremist monitoring group, also threatened Western companies and the Algerian government.

The attack recalled a deadly hostage-taking at another Algerian gas plant in 2013, which left 37 dead.