More than 90 Afghan asylum seekers have broken out of the Darwin detention centre and are holding a mass protest on the side of a busy road.

The asylum seekers are holding signs which read: "Please help us", "Show us mercy", and "We are homeless, defenceless and we seek protection".

Two of the asylum seekers have told the ABC they are from Afghanistan and have been waiting up to nine months in detention.

They say they arrived by boat and have now been refused refugee status in Australia.

"Every week, every day, we going to die," one of them told the ABC.

"Nine months we here because that's why I want to go out to talk with you, all of the population of Australia.

"I need your help.

"My children aren't safe in this place; we don't know where is our family."

The situation is relatively calm, however the asylum seekers have gathered along the side of the Stuart Highway at Berrimah yelling out to media crews.

Immigration Department spokesman Sandi Logan says the department is concerned the men were able to escape the facility.

"There is a perimeter fence that they have pushed over and pushed through," he said.

'Pressure cooker situation'

Opposition immigration spokesman Scott Morrison says the Government's policies have created overcrowded detention centres.

"What we are seeing up in Darwin is of great concern," he said.

"This is a pressure cooker situation."

He says the Opposition has sought a briefing on the incident, but the Government has refused the request.

"What all this is symptomatic of is a detention network which has been pushed to complete breaking point," he said.

"There are more than 4,100 people who are now being detained by the Department Immigration and Citizenship as a result of Labor's failed policies.

"This is the highest level of number of people being detained by the department in our history."

Northern Territory Police say they are gathering their resources in preparation to remove the detainees.

Duty Superintendent Louise Jorgensen says the protest is peaceful.

"We received a call that the number of detainees had breached the security, gone out the fence," she said.

"It would appear that they've got together in a group ... and they're peacefully protesting their situation."

She says police will move the men if they do not agree to go back inside.

"They're peacefully protesting and we'd like to keep it that way," she said.

"We don't want to cause any agitation or any unrest so we're giving them every opportunity to have their protest and then get back in the detention centre."

Another riot, also involving up to 100 people, broke out at the Darwin centre over the weekend.

The Immigration Department says the weekend protest began when two men climbed a tree and refused to come down, and escalated to involve the majority of the Indonesian crew members being detained in the centre for alleged people smuggling.