The South African government is holding discussions with a “second country” on what action to take following the murder of an aid worker in Afghanistan, a foreign affairs spokesman said on Monday.

“As soon as discussions are concluded with the second country we will advise the nation (South Africa) what course of action will be taken,” Ronnie Mamoepa said.

He said the government was aware that the victim, Gayle Williams, had dual South African and British citizenship.

“We are aware that she had dual citizenship and we are in contact with the second country with regard to this matter.”

Mamoepa would not confirm the “second country’s” identity. The South African government extended its condolences to the bereaved family.

Earlier the British Press Association reported that Williams was apparently murdered because she was a Christian, She was shot dead by gunmen on a motorcycle as she walked to work in the capital, Kabul, about 8am local time on Monday morning.

She was a volunteer with British-registered Christian charity Serve Afghanistan, which primarily works with disabled people in the war-torn country.

The Taliban claimed responsibility for the shooting, saying Williams was killed because she was spreading Christianity.

But Mike Lyth, the Carlisle-based chairman of Serve Afghanistan’s board, rejected this explanation.

“They will make any excuse. They probably saw there was a Christian organisation operating in Kabul and thought, ‘this is how we can kill it’. We are Christians — that is what gives us the motivation to go into a dangerous and difficult country to try to help. But she was not involved in proselytisation.”

Lyth described Williams as a “lovely girl”, adding: “She was the life and soul of the party, a great adventurer. She will be sorely missed — a great girl.”

Afghan interior ministry spokesman Zemeri Bashary said the killers shot Williams in the body and leg with a pistol.

Lyth said: “She was walking to work… at 8am local time. “She was almost at the office when a couple of guys jumped off a motorcycle with some kind of weapon and shot her. She was dead almost immediately.

“One of our staff came on the scene fairly soon afterwards and found her dead. Now they are trying to live with the consequences of that. We are in deep shock about it all because we knew her very well.”

Williams, who was in her mid-30s, had been working for Serve Afghanistan for about two years and was considered an experienced and careful member of staff.

She was previously based in the southern Afghan city of Kandahar but was pulled out when it became too dangerous.

The aid worker spoke local languages Pashto and Dari, although not fluently, and got on well with the Afghan people, Lyth said. “It is a tragedy that she was killed in Kabul, which is supposed to be relatively safe,” he added.

“She was an experienced aid worker — she was not one who took undue risks.” Williams was brought up in South Africa but spent much time in Britain and holds dual nationality for the two countries, Lyth said. Her mother lives in the UK and she has a sister in South Africa. Serve Afghanistan has 15 expatriate members of staff, all volunteers, and employs 200 Afghans.

Lyth said the charity would now have to take a “long, hard look” at its operations. “I personally have been very concerned about security for a long time. But we have tried to take all possible measures to reduce the threat.

“We train our people really carefully, we are in daily touch with the security authorities to find out which roads we shouldn’t be on, which parts of the country we shouldn’t go to.”

He added: “Each time something like this happens, you wonder — do you go on exposing people to unnecessary risk? Yet at the same time you have got the cry of many, many of the Afghans saying ‘Please help us’. You’re caught between a rock and a hard place.”

International Development Secretary Douglas Alexander condemned the Taliban’s attempt to justify the killing as a religious act. He said: “It was with great sadness that I heard today about the death of Gayle Williams, a charity worker whose only aim was to help the people of Afghanistan.

“Her killing was a callous and cowardly act by people who would take Afghanistan back to the dark days of the Taliban tyranny which scarred the country for so long.

“Gayle and thousands of others like her are in Afghanistan to help ease the grinding poverty which afflicts millions of people. “To suggest her killing was a religious act is as despicable as it is absurd — it was cold-blooded murder.”

The killing will spark new fears about the safety of Western civilians working in Afghanistan — but it is not the first. In August, aid worker Dr Jacqueline Kirk, 40, who had dual British and Canadian nationality, was gunned down with three other International Rescue Committee workers.

They were travelling through Logar province in the east of the country in clearly marked humanitarian vehicles.

Attempting to convert people to another religion is illegal in Afghanistan, and militants have targeted Christians in the past. A group of 23 South Korean church volunteers were kidnapped in southern Afghanistan in July last year. Two were killed before the others were released unharmed.