A Pakistani cleric who accused a young Christian girl of blasphemy in a case that sparked international concern was remanded in custody Sunday on suspicion of evidence-tampering and desecrating the Quran.

The girl, Rimsha, has been held in prison since being arrested in the poor Islamabad suburb of Mehrabad more than two weeks ago accused of burning papers containing verses from the Koran, in breach of Pakistan's strict blasphemy laws.

A medical report last week said she had a mental age of less than 14 and her case has prompted concern among Western governments and anger from rights groups who say Pakistan's strict blasphemy legislation is often abused to settle personal scores.

Hafiz Mohammed Khalid Chishti, the imam of the mosque in Rimsha's area, who first gave police the burned papers as evidence against her, was detained by police on Saturday evening.

"The imam was arrested after his deputy Maulvi Zubair and two others told a magistrate he added pages from the Koran to the burnt pages brought to him by a witness," police investigator Munir Hussain Jaffri said.

Zubair and the two others, Mohammad Shahzad and Awais Ahmed, said they had urged Chishti not to interfere with the papers, Jaffri said.

"They protested that he should not add something to the evidence and he should give the evidence to the police as he got it and should not do this," Jaffri said.

"But they said Chishti said, 'You know this is the only way to expel the Christians from this area.'"

On August 24 Chishti told AFP he thought Rimsha had burned the pages deliberately as part of a Christian "conspiracy" to insult Muslims, and said action should have been taken sooner to stop what he called their "anti-Islam activities" in Mehrabad.

Jaffri said the cleric was arrested at his home on Saturday under the blasphemy law.

"By putting these pages in the ashes he also committed desecration of the Holy Quran and he is being charged with blasphemy," he said.

Rimsha's lawyer Tahir Naveed Chaudhry said the case against her was fatally flawed.

"This development has created doubts and under the law, the benefit of the doubt is always given to the accused," he told AFP.

"Now it has been fully proven that it was a conspiracy. We want that Rimsha should be acquitted immediately."

Chishti, who arrived at court on Sunday blindfolded and handcuffed and guarded by armed police commandos, was remanded in custody for 14 days and will be held at the same jail as Rimsha.

Speaking to reporters, Chishti said the allegations against him were "concocted".

Rao Abdur Raheem, the lawyer for Rimsha's accuser, her neighbour Hammad Malik, said the development was intended to "spoil" his case and he accused the authorities of interfering.

"They are pressurising the complainants and witnesses to facilitate the bail of Rimsha," he told the court.

"They are making threats on behalf of the people sitting in the president's house."

A medical report earlier this week said Rimsha appeared to be around 14 years old, which would make her a minor, and had a mental age below her true age, but the court has yet to decide whether to accept the assessment.

Some reports have said Rimsha has Down's Syndrome.

She is being held in a high-security jail in Islamabad's twin city Rawalpindi and on Friday a judge extended her remand for another two weeks.

On Sunday around 150 Christians and rights activists held a protest march in Rawalpindi calling for Rimsha's release.

Blasphemy is a very sensitive subject in the Pakistan, where 97 percent of the 180 million population are Muslims, and allegations of insulting Islam or the Prophet Mohammed often prompt a furious public reaction.