The Islamist militants Boko Haram have unleashed a new wave of attacks amid mounting criticisism of President Goodluck Jonathan trip to Brazil for a UN conference.
Police say at least 34 civilians and six security officers were killed in sectarian violence that engulfed Damaturu, in Nigeria's northeast.
The death toll is expected to rise as rescuers continue to search for the wounded and the dead.
The city was deserted Wednesday. The government imposed a round-the-clock curfew that left residents trapped wherever they were when violence erupted.
Across the city, people are running out of food, medicine and water.
Meanwhile, the Action Congress of Nigeria (ACN) criticised the President Goodluck Jonathan for going to Brazil to attend the United Nations Conference on Sustainable Development, after the country was rocked by another series of bombings in Kaduna state on June 17, where suicide attacks in two churches killed at least 21 people in the city of Zaria, Kaduna state.
In a statement issued in Lagos on June 19 by its National Publicity Secretary, Alhaji Lai Mohammed, said: "The usual thing is for leaders to cancel foreign trips or rush home from such trips when their countries suffer tragedies", the statement read.
The House of Representatives also criticised the move, saying the president could have sent Vice President Namadi Sambo or another senior top aide to the conference.
"A trip like that could have been delegated by Mr President so that he can stay at home to take charge of security", the spokesman for the House, Zakari Mohammed told the Nigerian CKN Nigeria.
"We know that security agencies are supposed to do their job, but we cannot afford to compromise security. If our security is compromised, it is a failure of governance," he added.
Another representative Olajumoke Okoya-Thomas also complained about the president's handling of the situation, saying: "We should issue marching order to the President in view of the security situation"
Other political parties, including the Congress for Progressive Change (CPC), and the All Nigeria Peoples Party (ANPP) also condemned the move.