Two suspected suicide car bombers attacked the offices of two major telecoms companies in the volatile northern Nigerian city of Kano on Saturday, police and the army said.
One of the attackers blew himself up when he rammed his car into the office gate of the Airtel mobile phone company, setting the building ablaze, police said.
There was no immediate claim of responsibility for the attacks in northern Nigeria's largest city, and no reports of any civilian deaths.
The Islamist group Boko Haram -- notorious for shootings and bomb attacks across north and central Nigeria -- has in the past targeted phone companies, accusing them of cooperating with the security services.
"There has been a bomb blast at Airtel office. From what we hear, it was a suicide attack. The bomber rammed his car into the gate and blew himself up. The building is on fire," said a policeman who requested anonymity.
The attack was confirmed by an army spokesman in Kano, Lieutenant Iweha Ikedichi.
Airtel worker Bayo Osho said his leg was injured in the blast.
"A car rammed into the gate and forced its way into the premises. The car hit me on the leg and flung me into a corner before it exploded. I was dragged out and taken to the hospital by soldiers outside the gate," he told AFP at the hospital where he was taken for treatment.
Security agents cordoned off the scene while firefighters battled to put out the fire.
Officials from Airtel, one of the three biggest mobile phone service providers in Nigeria, were unavailable for comment.
A second suspected bomber was blown up when his car exploded outside the gate of an office of MTN, the country's largest mobile network, was blown up when his car exploded outside the gate, Ikedichi said.
No other casualties were recorded in the attack, he added.
Kano was the scene of Boko Haram's deadliest attack yet in January, when at least 185 people were killed in coordinated bombings and shootings.
Violence linked to the Boko Haram insurgency is believed to have left some 3,000 people dead in Nigeria since 2009, including killings by the security forces.