The attackers bombed a city police headquarters, three other police stations and several churches in Damaturu, north east of Nigeria, late Friday after similar raids in another city that had already been the target of attacks by an Islamist sect.
A lawyer who visited Damaturu's government hospital Saturday looking for a missing friend said he counted 60 bodies in the morgue.
"I have seen 60 dead bodies in the hospital, all brought in yesterday from the attacks," the lawyer, who asked not be named, told AFP by telephone.
"I am here to look for my friend who didn't return home yesterday."
He said anxious relatives were flocking to the hospital in search of loved ones.
A senior local government official in the city, who said he did not have permission to speak to the media, told AFP that the hospital was full to the brim with the injured following Friday's attacks.
"The general hospital is full with people who were injured in the attack. If I say there are hundreds injured, it's not an over-estimation. Everywhere is full with the injured," he said, without giving a death toll.
The authorities were not immediately available for comment.
Gunmen bombed police posts and churches in the city before engaging in gun battles with security forces, hours after a lunchtime suicide attack targeted an army base in the city of Maiduguri, also in the northeast.
No group has claimed responsibility for the attacks, but residents of Damaturu suspect the Islamist sect Boko Haram, which is based in Maiduguri.
The police headquarters in Damaturu, just west of Maiduguri, appeared to have been one of the first and main targets of the attacks.
A mason working there at the time of the attack said he saw bodies of five policemen as he made good his escape after the bomb went off.
"I was plastering a building in the police headquarters when I heard a loud blast. I was thrown to the ground, and the window I had just fixed was blown up from the impact of the blast. I believe I saw five dead men. ... They were men in police uniform," Adamu Mohammed said.
He said he saw several others injured as he scaled a fence to flee the scene.
Nigeria's north is predominantly Muslim, with pockets of Christian communities.
In a mainly Christian neighbourhood called Jerusalem, six churches were bombed in addition to a police station.
"A police station and a mechanical workshop of the police were attacked. Six churches in the area were also bombed," said resident Edwin Silas, adding: "The whole city is traumatised."
Soldiers and police have mounted checkpoints in parts of the city, searching vehicles and carrying out pat-downs of drivers and passengers.
In the town of Potiskum, a grenade narrowly missed a police station and an ensuing gun battle left one policeman dead.
The string of attacks came two days ahead of the annual Muslim celebration of Eid al-Adha, or the Feast of Sacrifice, and police have been put on red alert nationwide.
Militants from Boko Haram, whose name means "Western Education Is Sin" in the regional Hausa language, have targeted police and military, community and religious leaders, as well as politicians, in scores of attacks in recent months.
The sect, which wants to see the strict application of Sharia or Islamic law, staged an uprising which was brutally put down by security forces in 2009.
It claimed responsibility for the August 26 bombing of the UN headquarters in the capital Abuja which killed 24 people, as well as a June attack on the national police headquarters, also in the capital.