Tributes have been paid to a Stevenage doctor who was killed following an ambush by gunmen in Afghanistan.

Dr Karen Woo, 36, was one of 10 aid workers killed by insurgents while working for International Assistance Mission (IAM), a non profit-making Christian organisation. It is believed they were executed, while pleading for mercy returning to the capital Kabul after returning from a mission helping youngsters with eye problems.

A statement on the IAM website said: “This tragedy affects our ability to continue serving the Afghan people. We hope it will not stop our work that benefits more than a quarter of a million Afghans each year.”

As tributes poured in an unnamed quote in tribute to the Stevenage medic said: “She was a beautiful soul and had such a big heart. We will miss her in Kabul.”

Among posts on Facebook, her cousin Lorraine Nugent wrote: “My beautiful, brave, caring cousin Karen Woo has been killed delivering aid and medical care in Afghanistan. Why? She was there because she cared about others.’’

It is believed that Dr Woo was due to fly home to marry security contractor Mark Paddy Smith, a man she had met in Afghanistan, in a ceremony in Chelsea.

Her family have been too upset to comment on the tragedy. Her father Tehaun Woo, 67, an engineer, and mother Lynn, 66, a former nurse at Lister Hospital were believed to have been planning the register office wedding this week.

Reports suggest that Dr Woo and her colleagues, six Americans, a German doctor and two interpreters, were marched from their vehicles and shot on Friday. It is not known yet whether the atrocity was the work of the Taliban or the actions of robbers on what was thought to be a safe road back to the capital. Only one person, a Muslim in the convoy, is thought to have survived the attack. The Taliban have claimed responsibility for the attack.