(CNN) -- Al Qaeda-linked militants have banned three international aid groups from working in Somalia, claiming they are "actively propagating Christianity" in the predominantly Muslim nation.
Al-Shabaab, the Islamist militant group battling Somalia's U.N.-backed transitional government, ordered World Vision, Adventist Development and Relief Agency and Diakonia to cease their operations.
"Acting as missionaries under the guise of humanitarian work, the organizations have been spreading their corrupted ideologies in order to taint the pure creed of the Muslims in Somalia," the militant group said in a statement Monday.
"Along with their missionary work, the proliferation of corruption and indecency has become prevalent as a result of their presence," the statement said, warning other non-governmental groups against engaging in "similar activities"
All three organizations are Christian aid groups. However, as signatories of the International Red Cross and Red Crescent Movement code of conduct, they have specific polices against proselytizing when distributing aid.
World Vision -- which serves about 100 million people in nearly 100 countries around the world -- said it was "surprised and disappointed" by Al-Shabaab's order. The group said it is motivated by its faith to help those living in poverty, but is impartial when handing out aid.
"World Vision Somalia received a demand today from Al-Shabaab to close operations in Somalia," World Vision said in a statement Monday. "World Vision guards were disarmed and their keys were taken. Nothing was removed from the offices although Al-Shabaab representatives occupied the offices."
The group said its operations in south central Somalia have been temporarily suspended as "we plan our next steps."
ADRA said its work in Somalia as solely focused on implementing emergency relief and development since 1992. More than 650,000 Somalis benefited from the group's humanitarian work in 2008, the group said in a statement.
"ADRA remains committed to serving the people of Somalia as circumstances allow," the group said.
There was no immediate response from Diakonia, a joint international development organization of five Swedish churches. According to its website, the group has regional offices in Africa, Asia, the Middle East and Latin America and has aid operations in Somalia.