LUSAKA (Reuters) - Zambian health authorities have withdrawn a hard-hitting anti-AIDS campaign from state radio and television after church groups said it encouraged promiscuity and moral decay, officials said on Wednesday.

"The adverts are off air," said an executive from the state Zambia National Broadcasting Corporation.

"They were withdrawn on the instructions of the Central Board of Health (CBoH)."

The graphic nationwide broadcasts urged Zambians to practise safe sex by using condoms. It aimed to curb the spread of HIV/AIDS, which has infected one in five Zambian adults and is the country's biggest development challenge.

The Catholic Church and the umbrella church group Christian Council of Zambia had urged the government to withdraw the adverts, saying they were in bad taste and appeared to condone sex if one used a condom.

"We do not believe the adverts on TV are meant to curb the spread of AIDS. They show the young people that it is alright to have sex, but you prevent infections by using a condom," said Christian Council spokewoman Ing'utu Mutembo.

An executive from the state broadcaster told Reuters that the government wanted to amend its anti-AIDS message to encourage abstinence.

The ban flies in the face of Health Minister Enock Kavindele's comments on Monday that the campaign would not be withdrawn.

"I have told religious leaders that the prospect of preaching to empty churches is very high if we do not deal with AIDS firmly. The adverts might be offensive, but we must face reality," Kavindele told Reuters.

Kavindele was not available for comment on Wednesday. AIDS activists suggested that the CBoH - which is autonomous and acts as chief adviser to the minister--had taken the decision and would brief Kavindele on its reasons later.

Sub-Saharan Africa is at the epicentre of the global HIV/AIDS epidemic, which affects about 70% of the region's 34 million people.