A minority Muslim group has been ordered to convert to Sunni Islam or face expulsion in Indonesia.
The move by Bangka-Belitung, made up of two main islands off South Sumatra, is the latest in a series in which religious minorities including Christians and Shi'ite Muslims have faced harassment and complained of a lack of protection.
"The Ahmadiyah have a right to live in Bangka," Fery Insani, a senior official in the local government, told Reuters.
However he said: "In a meeting with community leaders and religious figures, all of us have agreed that it is forbidden for them to conduct activities like spreading their faith."
The Ahmadiyah self-identify as Muslim and follow the teaching of the Qur'an but regard an Indian preacher, Mirza Ghulam Ahmad, as a "messiah" who came after the Prophet Muhammad. This belief is considered heretical by Indonesia's mainstream Muslim population which is the largest in the world.
"The Ahmadiyah congregation are not allowed to spread their religion," said Bangka Island's most senior bureaucrat in a letter seen by Fairfax Media. "Ahmadiyah followers in Srimenanti village must immediately repent in accordance with Islamic sharia that there is no prophet after the prophet Muhammad." He said if they did not follow this ruling, a meeting had decided they must immediately leave Bangka and return to their place of origin.
The threat marks an ongoing persecution against minority religious groups from Indonesia's hardline Muslims despite the fact the constitution guarantees religious freedom.
Around 1,000 members of a group called Gafatar were evacuated from their homes following violence in West Kalimantan last week and authorities have banned the minority group which they describe as radical and dangerous. This came after hundreds of Muslims forced the local government to tear down several churches in the conservative province of Aceh last year, claiming they lacked proper building permits.
"We hope the police can guarantee security for the Ahmadiyah people in Bangka and that the local government guarantee our rights as citizens," said Yendra Budiana, a Jakarta-based spokesman for the Indonesia Ahmadiyah Community.
A spokesman for the religious affairs ministry declined to comment on the issue.
Additional reporting by Reuters.