An 11-year-old girl with Down's Syndrome is being held on blasphemy charges after being accused of burning pages of the Quran as she apparently gathered paper as fuel for cooking.

The Christian girl, known only as Rimsha, was arrested on Thursday after she was reportedly seen in public holding burnt pages which had Islamic text and Koranic verses on them, a police official told AFP.

A police officer involved in the case, in Pakistan's capital Islamabad, said the accused girl had told him she had no idea there were pages of the Quran inside the papers she had burnt.

Qasim Niazi said the girl was illiterate and had not attended school, although there conflicting reports as to her mental state. He also told CNN 150 people had gathered in a part of town where the Christian population is based and threatened to burn down their houses.

He said: "The mob wanted to burn the girl to give her a lesson." He added families in the area had fled in fear.

Paul Bhatti, Pakistan's minister for National Harmony, told the BBC that it was "unlikely she purposefully desecrated the Koran".

"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."

A statement from President Asif Ali Zardari called for an urgent investigation into the incident and insisted vulnerable sections of society must be protected "from any misuse of blasphemy law", Pakistan's Dawn newspaper said.

"Blasphemy by anyone cannot be condoned but no one will be allowed to misuse blasphemy law for settling personal scores," the president's spokesperson Farhatullah Babar said.