Explosions at two police stations in the northwest Nigerian town of Sokoto have killed at least two people, witnesses and police said.
Officials said the blasts on Monday at the Yan Marina police station in the city centre and the Unguwar Rogo station were both caused by suicide bombers.
Up to 30 people were injured in the blasts, the Red Cross said.
Separately, police guarding a home belonging to Vice President Namadi Sambo came under fire from gunmen in the northern city of Zaria, leaving one civilian dead.
No one lives at the house, which is undergoing repairs from damage inflicted in post-election riots last year.
Nigeria's mainly Muslim north has suffered an upsurge in violence over the past year, much of which has been blamed on the hardline Boko Haram group.
The group is suspected of having hideouts in Sokoto, but it has rarely struck within the city.
A Red Cross official, speaking on condition of anonymity, told the AFP news agency "a policeman and woman were killed in the bombings. Thirty people were injured, mostly around the market in the Yan Marina neighbourhood."
Usman Bube, a Yan Marina resident, said the area was "engulfed in flames".
"There was a huge explosion about an hour ago at the police station that was followed by thick smoke," Bube told AFP. "It is so chaotic now, with people running to safety."
A senior police officer, who did not want to be identified, said the bomber approached the station in a vehicle packed with explosives and was denied entry at the security gate, where the vehicle then blew up.
Lawai Danfili, who lives near the Unguwar Rogo station, said residents raced into their homes following the attacks.
"We had a loud explosion around the police station. The impact of the explosion shook houses in the area. We all moved indoors," he said.
While there was no immediate claim of responsibility, Boko Haram has repeatedly targeted police across northern Nigeria, where most of its attacks have been carried out.
In May, gunmen accused of being Boko Haram members shot at a building near the Yan Marina police station, killing one officer and a civilian.
The group has been blamed for the deaths of more than 1,000 people in attacks since mid-2009 and three of its top leaders have been designated as global terrorists by the United States.