In the Kano incident Monday, bombers reportedly drove explosives-filled vehicles into a luxury bus at a motor park in Sabon Gari used by people traveling to southeastern or eastern Nigeria, the Nigerian Tribune reported Tuesday.
Officials said the suicide bombing involved five buses owned by three private mass transit firms. The car struck a fully loaded bus, resulting in an explosion and fire that engulfed the other vehicles.
More than 50 other people, mostly itinerant workers, were injured.
Motor park attendant Ade Ola told Leadership Newspapers the suicide bombers approached in their vehicles as if they were passengers rushing to board one of the buses.
"Many of us saw the suicide bombers coming in two different ... cars," Ola said. "One stopped in between the four buses and the other stopped at a distance. We thought them to be passengers. The first bomb exploded before the other."
Another witness said he saw "bodies littering everywhere. People were burning; people were crying; people were running helter-skelter."
While no one claimed responsibility, authorities said the militant Boko Haram is a prime suspect, the Tribune said.
President Goodluck Jonathan condemned the blast, saying in a statement "the barbaric incident will not deter the federal government from its strong-willed determination to overcome those who do not mean well for this nation."
In the Borno state incident, an elementary school in an insurgent stronghold was attacked Monday, killing a teacher and two students, officials said.
One resident told the Tribune the area was prone to militant attacks "but not on small children."