Two men detonated the explosives concealed under their clothes as soon as they got off the bus at Kano Line motor park Tuesday afternoon, Police Commissioner Ibrahim Idris said. The busy station is located in the city center of Kano.
Idris said the two men took the bus from the town of Wuddil, 30 kilometers (about 19 miles) from Kano.
"The bus station was their target, and taking a bus from outside the city gave them easy access into the bus station," Idris said, explaining that the men "would have undergone screening before getting inside if they had come by any other means."
The attack occurred at 3 p.m. local time, just hours after another suicide attack left 17 people dead, in addition to the bomber, and 27 people injured at a bus station in Potiskum, about 200 miles away in Yobe state.
The Potiskum attack occurred at Tashar Dan-Borno motor park on the outskirts of town. A man pretending to be a passenger detonated the explosives as he boarded the bus, which was being loaded and prepared for departure, according to witnesses.
An official at the Potiskum motor park said 12 passengers were inside the bus when the bomber, who "looked to be in a hurry" came and dropped his luggage in the baggage compartment.
The man "made to enter the bus, but before he could be restrained for routine screening there was an explosion which killed all 12 people inside the bus and the bomber," the motor park official said.
A paramedic at Potiskum General Hospital, who asked not to be named for fear of reprisals, said four people who were transported from the scene died later.
Resident Ahmad Maina, who was at the scene shortly after the blast, said the bus was engulfed in flames as firefighters struggled to keep it from spreading to other vehicles.
Cities repeated targets of Boko Haram terror
Although no one has claimed responsibility for either of the attacks, Boko Haram has been behind dozens of suicide and other bombings in northern Nigeria.
Potiskum, the commercial hub of Yobe state, has been hit repeatedly in recent months by bombings blamed on the extremist Islamist group.
On Sunday, a 7-year-old girl blew herself up outside a cell phone market in the town, killing seven people and injuring 11. Last month, two suicide bombers killed six people and injured 37 at the same market.
Likewise in Kano, northern Nigeria's most populous city, suicide bombings in the past year have targeted schools, gas stations and a market.
Boko Haram's stated goal is to bring an extreme version of Sharia law to the masses. Along with suicide bombings they have attacked churches and mosques, raided once-peaceful villages and kidnapped people young and old, most infamously more than 200 girls taken last April from a school in Chibok.
More than 150,000 people have fled into neighboring countries as a result of the violence, according to the United Nations refugee agency, and Boko Haram has spread its reign of terror into villages and towns beyond Nigeria's borders. Currently, thousands of Chadian troops are in Cameroon helping that nation's military root out Boko Haram fighters.