Image caption Christians argue they are often falsely accused of blasphemy

Pakistan's president has ordered a report into the arrest of a young Christian girl, reportedly with mental impairments, accused of desecrating pages of the Koran.

Police say the girl was arrested last week in a Christian area of the capital, Islamabad, after a furious crowd demanded she be punished.

Officials said the girl could not properly answer police questions.

Her parents have been taken into protective custody following threats.

Many other Christian families have fled the neighbourhood after unrest erupted. Reports say that police arrested her under pressure from the large crowd.

But there are conflicting reports about the details of the incident.

It is unclear whether the girl burned pages of the Koran or if she was found with pages of the Koran in a bag.

Christian leaders say she is as young as 11 but police quoted in some media reports also say she may be older and that she had no mental impairments.

She is an innocent child - she doesn't even know what she did. She is in a state of shock Xavier P William, Human rights activist The girl's 'trauma'

Some Christian groups suggested that the girl has Down's syndrome, which is a congenital condition that causes various degrees of learning difficulties and certain physical abnormalities.

State media said that President Asif Ali Zardari had "taken notice" of the reports of the arrest and asked Pakistan's interior ministry to present a report to him.

Controversial laws

The incident comes amid a debate about Pakistan's strict anti-blasphemy laws.

Rights activists have long urged Pakistan to reform the laws, under which a person can be jailed for life for desecrating the Koran.

Many of those accused of blasphemy have been killed by violent mobs, while politicians who advocate a change in legislation have also been targeted.

Analysis Social media have been at the forefront of the condemnation of the latest arrest, which has revived the old debate over the country's strict blasphemy laws. But it is notable that the government has stayed silent on the issue. Interior Minister Rahman Malik on Sunday chose to speak for more than 30 minutes on allegations made against Pakistan by India but did not touch on this case. And despite the voices of outrage, many people do in fact support these laws. Even if the girl is found innocent in this case, analysts doubt if any government will have the courage to address the blasphemy law.

Last month, an angry crowd seized a man accused of blasphemy, and who was also said to be mentally unstable, from a police station and burnt him to death in the Bahawalpur area of Punjab province.

Last year, Shahbaz Bhatti, the minister for minority affairs, was killed after calling for the repeal of the blasphemy law.

His death came just two months after the murder of Punjab Governor Salman Taseer, who also spoke out about the issue.

Paul Bhatti, Pakistan's minister for national harmony, earlier told the BBC that the girl was known to have a mental disorder and that it seemed "unlikely she purposefully desecrated the Koran".

Pakistan's blasphemy laws After partition in 1947 Pakistan inherited offences relating to religion, which were first codified by India's British rulers in 1860

In the 1980s clauses were added to the laws by the military government of General Zia-ul Haq

One clause recommends life imprisonment for "wilful" desecration of the Koran. Another says blasphemy is punishable by death or life imprisonment

Muslims constitute a majority of those booked under these laws, followed by the minority Ahmadi community

A majority support the idea that blasphemers should be punished, but there is little understanding of what religious scripture says as opposed to how the modern law is codified Q&A: Pakistan's controversial blasphemy laws

"From the reports I have seen, she was found carrying a waste bag which also had pages of the Koran," he said.

"This infuriated some local people and a large crowd gathered to demand action against her.

"The police were initially reluctant to arrest her, but they came under a lot of pressure from a very large crowd who were threatening to burn down Christian homes."

The BBC's Orla Guerin visited the poor slum neighbourhood where the incident took place. Many Christian families have fled the area and although some men have returned to their homes, a sense of unease remains, our correspondent reports.

Police said they had no choice but to intervene, saying the angry crowd was threatening to set the girl alight.

Rights groups have condemned the arrest. The Women's Action Forum (WAF) demanded the girl's immediate release and expressed outrage at the "total inhumanity" of those who lodged the case with police, AFP reports.

WAF said the case should have been dealt with under the juvenile justice system.