Bodies remain strewn about the streets of a northern Nigerian town two days after Boko Haram militants launched a swift attack, residents told local officials. 

Borno state senator Ahmed Zanna said there were a "lot of killings" since Boko Haram ascended on Bama town on Monday, the BBC reported. Government forces expelled the rebels that same day but they returned with more fighters and seized the town on Tuesday, he said.

Rebels from the Islamist militant group kept watch on the streets, preventing residents from collecting the dead.

"So many bodies litter the streets, and people are not allowed to even go and bury the dead ones. So the situation is getting worse and worse," Zanna told the BBC.

But on Wednesday the government said Bama was not under rebel control.

"The attack on Bama town...was very unfortunate, but I want to reassure our people that government is on top of the situation," Borno state Deputy Governor Zanna Mustapha said according to Reuters. "Our security forces are engaging the insurgents in a fierce battle."

Bama, if it is seized, is just one Nigeria's many northern towns affected by Boko Haram, which the U.S. declared a terrorist group in 2013.The group, whose name means "Western education is forbidden," has waged a violent campaign across the north in an attempt to establish a caliphate.

About 26,000 people have been displaced by fighting in Bama, which used to have some 270,000 residents, according to the BBC.

Bama's seizure raises fears the rebels are closer than ever to attacking Maiduguri, Borno's capital with a population of over two million. The capital's government already moved up the city's existing curfew from 10 p.m. to 7 p.m.

Zanna told the BBC it would be "catastrophic" if Maiduguri fell.

"I'm begging the government to send more troops and armory to Maiduguri," he said.