Two suicide bombers in separate cars carried out the attack Saturday, the Daily Trust reported.
Both drivers drove cars filled with explosives into the Airtel building, causing a massive fire, said Bayo Osho, an Airtel staff who survived the attack.
Joint Task Force officers cordoned off the building and fire fighters were battling the blaze.
Vanguard newspaper said it was unclear how the bombers gained access to the building.
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