Suicide car bombers today attacked the offices of a Nigerian subsidiary of Indian telecom major Bharti Airtel in the volatile city of Kano besides that of South African firm MTN, killing at least four.
Survivor Bayo Osho said they were at work in the Airtel building located near Mallam Kalto Square in Sabon Gari when two suicide bombers drove separate vehicles into the premises.
According to the survivor, the first car was used to force the gate open and the driver came out and exchanged gun fire with the security personnel before the second one, laden with explosives, drove in.
The explosives went off and sent billows of flames and smokes into the air.
Firefighters have started battling to put of the fire even as men of the military Joint Task Force (JTF) have cordoned off the area.
Officials from Airtel, one of the three biggest mobile phone service providers in Nigeria, were unavailable for comment.
Reports also said that a office of MTN was also attacked by a suicide bomber.
A local news website, Street Journal said four persons died. But it was not immediately known if any civilians were killed. It was also not known where the casualties took place.
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.
Boko Haram says it wants to create an Islamic emirate in northern Nigeria.
The country has a population of 150,000, equally distributed among the two major religions - Islam and Christianity.
Muslims are mostly based in the north while the south has predominantly Christian population.
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