A pastor at the Seoul suburban church whose volunteers were taken hostage by the Taliban told parishioners on Sunday to brace for a spiritual fight against those who see its missions abroad as ill-conceived.

Nineteen South Korean Christians held hostage for six weeks in Afghanistan returned home to an uncomfortable welcome on Sunday, thanking their government for saving them from death.

"The Saemmul Church is at the centre of a war against our will," pastor Park Eun-jo said in a message to parishioners.

About 1,300 crammed into services at the church on Sunday. Many were overjoyed at the hostages' return but worried about a torrent of criticism unleashed at the church for sending missionaries to an obvious danger spot.

"Difficult situations will not be a problem if God is with us," Park said at the service.

The church is in negotiations with the government over who will pay the costs incurred in securing the release. One church leader said Saemmul had agreed to pay for the return air tickets and medical expenses.

Park, however said it was not right for the government to ask for compensation.

"The government never told us not to go there (Afghanistan)," Park said.

However, Seoul had warned evangelical Christian groups not to go to Afghanistan due to safety concerns and posted signs at its main international airport advising against travel to the war-torn country.

Park said he had heard that the two hostages killed by the Taliban died as martyrs.

Taliban insurgents kidnapped 23 from the church in mid-July. It shot two male hostages as initial negotiations stumbled and last month released two women captives.

"It is difficult to forgive the Taliban but let us forgive them through God's love, although we will remember," one church member said in leading the congregation in prayer.

Saemmul, set up about nine years ago, is one of several new evangelical churches in South Korea which see sending volunteers abroad as a testament to the strength of their congregation.

The number of South Korea Christian missionaries working abroad is second only to those from the United States.

Often, dozens or even hundreds of Korean evangelicals can be found abroad in a single small city fighting one another for exposure, the national daily Hankyoreh reported.

"We really need to reconsider what we are trying to do in missionary work," one member, who asked not to be identified, said after the service.