ALGIERS — Unknown attackers fired rockets on Friday at a gas facility in the Sahara in , the energy companies Statoil and BP said. There were no immediate reports of injuries.

The gas facility, Krechba, which is jointly operated by Statoil of Norway and BP of Britain, is overseen by the Algerian state-run gas company Sonatrach.

Statoil said the Krechba facility had been “hit by explosive munitions fired from a distance.” The company said it had been in touch with its three employees there, who were safe and had not been hurt.

BP said in a statement that there had been no reports of injuries to its employees and that the facility had been shut down as a safety precaution. It did not say how many people worked there.

Shots “were fired from outside into the facility,” the head of Statoil media relations, Bard Glad Pedersen, told the Norwegian broadcaster NRK. He said he did not know who had been behind the attack.

Krechba is part of the In Salah gas fields, about 750 miles south of Algiers, in the Hassi Messaoud region, a major gas-producing area in Algeria, about 440 miles from the border with Libya.

In January 2013, a band of militants affiliated with Al Qaeda , near the border with Libya. After a four-day standoff, the Algerian Army moved in and in the ensuing battle, at least 37 hostages, mostly foreign workers, died. The attackers were thought to have crossed into Algeria from Libya.

As in Krechba, the In Amenas facility is jointly run by BP, Sonatrach and Statoil.