The 15 hours of recordings include a fire chief’s appeal for army assistance, and a desperate plea by a civilian who was buried in a fire engine by the collapse of the first tower on September 11, 2001. “I can’t breath much longer. Please save me,” the man shouts into the radio. The emergency despatcher tells the man: “Calm down and relax. We do have somebody on the way.” It is not clear if the man survived.

The man’s cry for help is one of dozens of crackling recordings of people pleading for assistance from firefighters and ambulance crews who responded to the al-Qaeda attack by hijacked jets on the twin towers in New York.

As soon as the first plane hit the north tower at 8.46am, fire despatchers began sending all units to the site. As trucks arrived, the second plane slammed into the south tower and there were numerous reports of trapped civilians and injured firefighters.

For first time the public is able to hear the voice of Battalion Chief Orio Palmer, who climbed with a colleague higher up the burning towers than any other firefighters are known to have done.

Chief Palmer made it to the impact zone on the 78th floor of the south tower before the building collapsed. Once there the battalion chief reported “Numerous 10-45’s, Code Ones” — fire department code for dead people.

The mood suddenly changed when a fireman reported: “The tower just collapsed.” Immediately pleas for help start coming in. In the midst of the chaos, one fire chief cries into the radio: “We need the army in Manhattan!”

The release of the recordings was forced by a lawsuit brought by the New York Times and some of the firemen’s families.

Lee Ielpi, a retired fireman who lost his son Jonathan, a fireman, in the collapse, said that the families wanted to learn more about their loved ones’ final moments. “If I did hear his voice, it would be a godsend for me,” Mr Ielpi said. “I would like to hear his voice again.”

The fire department was reluctant to release the tapes for fear of causing further hurt to the families of the 343 firefighters killed.

“The department believes that the materials being released today . . . will serve to further confirm the bravery and courage of our members who responded to the World Trade Centre,” the fire brigade said. “It is the department’s hope that the release of these records will not cause our members and their families any additional pain.”

The fire department released 21 CD files of fire and ambulance communications and 500 oral histories gathered from firefighters who responded to the attack. The recordings run from 8.45am — a minute before the first plane hit the north towers — until 1.30pm, hours after both towers had collapsed, killing 2,749.

They may resolve questions about whether firefighters inside the north tower received an evacuation order before the second collapse.

Monica Gabrielle, a co-chairwoman of the Skyscraper Safety Campaign, whose businessman husband died, said: “Today we are one step closer to learning what happened on 9/11 in NYC — where we excelled, where we failed.”

At least one fire lieutenant said that he heard a call to evacuate while he was on the 35th floor of the north tower, and saw colleagues leaving.

“I was in the vicinity of the battalion chief, who was on the command channel, when I heard a mayday given over the command channel to evacuate the building,” Lieutenant Gregg Hansson said in his oral history. “I saw all the units get up, everybody got their gear, everybody started for the staircases.”

Paul Bessler recalled seeing a fellow fireman going up the stairs of the north tower as though he was “on a mission”. “Just at that point, my radio came clear as day, ‘Imminent collapse. This was a terrorist attack. Evacuate’.”

In the 12,000 pages of oral histories firefighters recounted the fear and confusion they felt as they arrived at the scene. “Somebody yelled something was falling,” firewoman Maureen McArdle-Schulman recalled. “It turned out it was people coming out and they started coming out one after the other. We didn’t know what it was at first, but then the first body hit and then we knew what it was.”

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