It went on to say that although some letters did not say what the consequences would be if Christians failed to comply, others are reported to have threatened bombing or the execution of all Christians. Police have increased security at churches, it said.

The unsigned handwritten letters were delivered to churches and Christian homes in the two towns on May 7th, giving a period of ten days for compliance, it added.

It said several Christian families have already fled since the letters were distributed. The news release quoted some Christians as saying that they knew the militants could kill them but they were trusting God for His protection. It further quoted them as saying that they would not yield to threats.

“These extremists are asking us to change our religion. We will not do it, even if we have to die”, the news release quoted All Pakistan Minorities Alliance Chief Shahbaz Bhatti as saying.

It said the Christians all over Pakistan will observe a period of prayer and fasting from May 17th (the date on which the ultimatum to the Christians expires) until May 27th.

Around 500 Christians live in Charsadda, where Islamic militants are using intimidation and violence to try to enforce a strict Islamic life-style, resembling that advocated by the Taliban in nearby Afghanistan, the news release said.

The militants’ bomb music shops, put pressure on barbers not to shave beards, and are trying to have girls' schools closed, it maintained.

It was in Charsadda that Pakistan's Federal Interior Minister, Aftab Ahmed Khan Sherpao, narrowly escaped death in a suicide attack last month which killed 28 people, it added.