Staff at Save The Children's eastern Afghanistan office had barely started work one cold Wednesday a year ago, when a car bomb tore through the street outside.

As employees at the British charity jumped from their desks to see what had happened, shots rang out and gunmen could be seen trying to get in through the shattered front gate.

Aid workers who usually spent the day providing health care, education and protection to children caught in Afghanistan's relentless war realised they were themselves under attack.

“The attackers just opened the doors and threw grenades then opened fire,” one employee told the Telegraph.

“When I and my friends saw the situation we rushed the basement. I saw six of my colleagues who were wounded. We were terrified and locked the door.”

Shut inside the basement bunker, staff could hear a gun battle raging above them and then the sound of attackers trying to get in.

“We all were counting the moments to our death, no one was breathing and we didn't expect to get out of the room alive,” another former worker said.