The premises of two mobile phone companies were attacked by suicide bombers in the northern Nigerian city of Kano on Saturday.
First, a bomber rammed a vehicle into the Airtel office, setting the building on fire.
Another attack was mounted minutes later on the office of MTN in the city, but the car failed to penetrate the perimeter fence.
The BBC reports no civilians were killed.
The Boko Haram group has previously targeted phone companies, accusing them of cooperating with the security services.
Boko Haram killed at least 185 people in Kano in January in a series of bombings and shootings.