"We have received information that terrorists will act against South Korea if they find South Koreans have entered Iraq for the purpose of propagating Christianity,'' South Korean Deputy Foreign Minister Lee Soo Hyuck told reporters.

After the beheading of South Korean interpreter and businessman Kim Sun Il last month, Seoul advised all civilians to leave Iraq.

The group that murdered Kim, Tawhid wa al-Jihad, or Unification and Holy War, posted a message on its website saying the killing was linked to religious activities of the firm that employed Kim, Gana Trading Co.

In a statement both in Arabic and English, the group said Kim, with degrees in the Arabic language and theology, wanted to be a Christian missionary in the Arab world.

The terrorist group said, "We killed him because he was a heretic who tried to spread Christianity in Iraq. The president of Gana Trading is also a sincere Christian. He contributes 10 percent of his earnings for missionary work and the company's name also comes from the Bible."

The terrorists had demanded that South Korea withdraw its troops serving in Iraq, but Seoul refused.

Along with its attempt to persuade citizens from traveling to Iraq, Seoul is trying to prevent South Korean Christians from attending peace rallies in Israel and the Palestinian territories Aug. 7-10 due to the threat of terrorism, Lee said, according to Bloomberg News.

Groups linked to the al-Qaida terrorist network said they will retaliate for South Korea's decision to deploy 3,000 additional troops in Iraq, Bloomberg reported.

South Korea has the third-largest presence after the U.S. and the U.K.