Two suicide car bombers attacked the offices of mobile phone operators India's Airtel and South Africa's MTN on Saturday in Nigeria's northern city of Kano, killing themselves but no civilians, police said.
Islamist sect Boko Haram has previously targeted phone firms, blowing up telephone masts and offices, saying the companies help the security forces catch its members.
"The one who hit the Airtel office was shot by military men before the bomb exploded ... at the MTN office the car rammed into the fence but no civilians were killed," Ibrahim Idris, the chief of police in Kano, told Reuters.
Airtel Nigeria's parent company Bharti Airtel, India's top cellphone operator, gave no immediate comment.
The national emergency agency confirmed the bombing and said it was not aware of any civilian casualties. The security forces have played down the death toll in previous bombings.
At least 2,800 people have died in fighting in the largely Muslim north since the sect launched an uprising against the government in 2009, watchdog Human Rights Watch says.
The sect wants to impose strict Islamic law on a country of 160 million people split roughly equally between Christians and Muslims.
The group has previously targeted churches on Christmas Day and security has been increased in all the major northern cities, although security experts say given the scale of Christian worship in Nigeria they cannot protect everyone.
Kano, Nigeria's second largest city after the southern commercial-hub Lagos, was the site of Boko Haram's most lethal attack which killed at least 186 people in January in coordinated bombings and shootings.