An ultimatum from the Syrian armed opposition's military chief caused over 1,000 Christians to flee the west Syrian town of Qusayr, adding to fears that believers may be forced out of Syria.

"The Christian communities fear being targeted, destroyed or driven out," said Neville Kyrke-Smith, Aid to the Church in Need's U.K. director. "We all need to stand in prayer and solidarity now."

Kyrke-Smith, who returned from Lebanon on June 11, told CNA that the report of Christian flight echoes the concerns he heard from bishops, priests, and religious communities concerned about Christians' fate in neighboring Syria.

"The message time and again was 'please do not forget the Christians of the Middle East,'" he reported.

Syrian opposition military chief Abdel Salam Harba had given an ultimatum for Christians to leave Qusayr, a town near Homs, by June 8. Some mosques in the city repeated the message in announcements from their minarets, Fides news agency reports.

Only 1,000 Christians remained in the town, which was home to 10,000 Christians before the conflict began between the Syrian government and opposition forces.

The reasons for the latest ultimatum are unclear. Some sources say it helps avoid more Christian suffering, while others say it reveals "a continuity focused on discrimination and repression." Others say Christians' open loyalty to the state is the reason they are driven away.

Some sources told Fides that Islamic Salafist extremists groups in the ranks of the armed opposition consider Christians to be "infidels" and are ready to start a "sectarian war."

The extremists reportedly confiscate Christians' goods and conduct executions.

Kyrke-Smith said that his organization has managed to provide some help to refugees from Homs, which witnessed an exodus of 50,000 or more Christians earlier this year. Other agencies and religious houses are giving refuge to Christians fleeing direct persecution.

He said there is "growing fear" that the conflict will expand and cross the border in to Lebanon and affect all communities.

"Christians are worried that they may suffer greatly as they could be targeted by all sides," he wrote in a June 10 blog post.

Gregorios III Laham, the Melkite Greek Catholic Patriarch of Damascus, has asked the Christian faithful to observe June 4 – 28 as a period of prayer, abstinence and fasting for peace.

"God can restore peace, brotherly love and mutual solidarity in Syria, in all its regions and among all its citizens," his message said. "This is our response to the painful events that have caused weeping and heartbreak, implanting terrifying images and causing hatred and revenge."