Pakistan's president Monday called on officials to explain the arrest on blasphemy charges of a Christian girl with Down's Syndrome who allegedly burnt pages inscribed with verses from the Quran.

There is a growing debate about religious intolerance in Pakistan, where strict anti-blasphemy laws make defaming Islam or desecrating the Quran punishable by death.

Police said the girl, Rimsha, was arrested in a low-income neighbourhood of the capital last Thursday and remanded in custody for 14 days after furious Muslims demanded she be punished.

Police, speaking to AFP on condition of anonymity because of the sensitivity of the case, said the girl was in her teens. Activists say she is 11 years old.

President Asif Ali Zardari took "serious note" of the arrest and called on the interior ministry to submit a report on the case, PTV said.

His government has been heavily criticised in the West for refusing to reform the anti-blasphemy law, despite the assassinations of a leading politician and a Christian cabinet minister who spoke out against the law in 2011.

Some reports suggested the girl had been burning papers collected from the rubbish for cooking when someone entered her house and accused the family of burning pages inscribed with verses from the Quran.

Human rights activists say the law is often used to settle petty disputes.

Muslim anger over the alleged incident forced Christians to flee the Mehrabad slum, home to hundreds of Christians 20 minutes' drive from Western embassies.

Rimsha's house was locked from the outside on Monday and no one was at home, said an AFP reporter. Neighbours were reluctant to speak about the incident, saying that they had not witnessed the alleged desecration themselves.

The streets were quiet as Muslims celebrated Eidul Fitr, the biggest celebration of their religious calendar, and one Christian neighbour told AFP that he had never left the area, not feeling any danger.

Local shopkeeper Mohammad Tahir said the girl was handed over to the authorities immediately after the incident "so that no one would hurt the family" and said there had been only a "very small protest" on Friday.

A senior official of the All Pakistan Minorities Alliance, Tahir Naveed Chaudhry, told AFP that Christians who fled for shelter with relatives elsewhere in Islamabad were now gradually returning to Mehrabad.

He said the girl had Down's Syndrome -- a condition which causes various degrees of learning difficulties -- and disputed the age given by police.

"She was just 11 to 12 years old," he said, adding his organisation wanted the hugely sensitive case resolved "amicably".

The Women's Action Forum, a leading Pakistani organisation fighting for the rights of women, condemned Rimsha's arrest.

Spokeswoman Tahira Abdullah demanded her immediate release and expressed outrage at the "total inhumanity" of the men who lodged the case with police.

Police should have dealt with the case under the Juvenile Justice System, she said, accusing police of not allowing lawyers to visit the girl.

Punjab governor Salman Taseer was assassinated in January 2011 and minorities minister Shahbaz Bhatti two months later for their opposition to the blasphemy law.

They had taken up the plight of a Christian mother sentenced to death for blasphemy in late 2010. She remains in prison.

Last month, a Pakistani mob snatched a mentally unstable man from a village police station and beat him to death in central Punjab province after he allegedly burned pages from a Koran.