The dead in Onitsha, mainly Muslims, were burned on bonfires of blazing tyres.
The violence flared in retaliation for the deaths of 15 Christians killed when Muslims turned on their neighbours in fury at highly publicised cartoons of the Prophet Mohammed.
On a drive around the town centre, civil rights workers saw at least nine more corpses to add to 19 they had found on Wednesday scattered by the road.
"We counted 60 bodies on Tuesday and 20 on Wednesday and there could be more," said Emeka Umeh, head of the local chapter of the Lagos-based Civil Liberties Organisation (CLO), adding "most of the victims are Muslims."
"It was a great massacre that should be condemned by any right-thinking person," he told AFP. "Even now, bodies can still be found on Upper Iweka road," which is home to the predominantly Christian Igbo people.
"The police should not relax. What we have now is graveyard peace," Mr Umeh added, saying the victims were slain "with machetes, knives, metal objects, clubs and in some instance, even guns."
The burned inner walls of Onitsha's central mosque were daubed with religious and political slogans such as "No Mohammed, Jesus is Lord."
Ifeanyi Eze, a smartly dressed 34-year-old businessman, picked a charred lump of timber from the wreckage, then scrawled on the mosque's outer wall: "Mohammed is a man, but Jesus is from above."
Asked why he felt the need, he replied: "We don't want to see all these Muslims anymore, because these are the people that cause all the trouble in world."
The Nigerian Supreme Council for Islamic Affairs (NSCIA), the country's highest Islamic body, condemned sectarian violence.
"There is a need to exercise restraint. Two wrongs do not a make a right. These rioters, be they Christians or Muslims, are pure extremists. The violence should stop, killings will not resurrect the dead and will solve no problem," NSCIA Secretary General Lateef Adegbite told AFP.
Oil worker hostages
Meanwhile Nigerian officials are pursuing talks with armed militants aimed at securing the release of nine foreign oilmen who were kidnapped six days ago from a barge in the Niger Delta.
The nine hostages, three Americans, a Briton, two Egyptians, two Thais and one Filipino, were seized on Saturday by separatist guerrillas during an attack on the energy giant Shell's Forcados oil terminal.