A church in South Africa is in mourning for its part-time pastor and his two teenaged children, killed in a suicide bombing in Afghanistan on Saturday.

Werner Groenewald, his 17-year-old son Jean-Pierre and a 15-year-old daughter, Rod^é, were killed after Taliban fighters attacked a house used by foreign aid workers. His wife Hannelie, a doctor, was working at a hospital when the attack began. An unnamed Afghan local also died in the attack.

Groenewald, 46, was in Afghanistan as part of an American-based educational charity, Partnership in Academics and Development (PAD), which helps educate poor and orphaned children in various countries in the Middle East and Central Asia. He became a pastor at the Moreleta Park Dutch Reformed Church in Pretoria 1997 and went to Afghanistan in 2002.

A statement on the church's Facebook page said: "The family was loved by the community and had stayed in contact over all these years.

"When the announcement of their murder was made on Sunday November it was received with great shock and sadness.

"It is not just a huge loss for the Moreleta Park community and for their close families, but also for the Afghan people whom they served with so much love."

Hannelie Groenewald's sister Riana du Plessis, who is acting as family spokeswoman, told AFP: "Their house was burned down. Hannelie went back there this morning to try to recover some of their goods, but there was nothing to recover. She lost everything - her children, her husband, her cats, her dogs."

A Taliban spokesman said on Twitter that the compound belonged to a secret Christian missionary group. However, the Groenewalds' friends and family denied that they were attempting to convert Afghans to Christianity.

The murders have raised awareness of the vulnerability of foreign aid workers in Afghanistan. Kabul has seen eight deadly suicide attacks against high-profile targets in the past 16 days. The head of a UK Christian organisation with workers in Afghanistan told Christian Today: "We have been very aware of heightened risks over the last year, and we have been operating on a very high security threshold."

He said that staff had regular meeting to assess security risks and that a set of objective indicators were used to evaluate the situation; for instance an attack on foreigners in their homes or places of work would mean that a particular threshold for action had been crossed.

"There are fairly standard protocols across all foreign NGOs," he said. "There is a lot of collaboration between them and regular security briefings."

The latest attacks, he said, might trigger a withdrawal by some organisations of their staff for a limited period.

He added that people who chose to work in Afghanistan were committed to the people there. "There is a desire to serve which is spiritually motivated. They are there to humbly serve the poorest of the poor."