KARACHI: More than 40,000 people rallied in Pakistan's southern city of Karachi on Sunday, police said, against the controversial reform of a blasphemy law that was behind the killing of a senior politician.

Religious groups blocked a main thoroughfare in Karachi's teeming metropolis holding banners in support of the police commando who shot dead Punjab governor Salman Taseer on Tuesday over his views in favour of the law's amendment.

Taseer had called for reform of the blasphemy law that was recently used to sentence a Christian woman to death. But his outspoken liberal stance offended the country's increasingly powerful conservative religious base.

“Mumtaz Qadri is not a murderer, he is a hero,” said one banner in the national Urdu language in support of the man who carried out Pakistan's most high-profile political killing in three years.

“We salute the courage of Qadri,” said another.

“There are at least 40,000 people here and more are coming,” senior police official Mohammad Ashfaq told AFP, watching over a sea of protesters bellowing slogans in favour of “jihad” and waving the flags of religious parties.

Another senior police official confirmed the number and said some 3,000 police officers were guarding the event, which had forced the closure of businesses and roads in the area.

Rally leader Qari Ahsaan, from the banned Islamic group Jamaat ud Dawa, addressed the crowd from a stage.

“We can't compromise on the blasphemy law. It's a divine law and nobody can change it,” Ahsaan told the masses.

“Our belief in the sanctity of our prophet is firm and uncompromising and we cannot tolerate anyone who blasphemes. Whoever blasphemes will face the same fate as Salman Taseer,” 40-year-old labourer Abdul Rehman told AFP at the rally.

Controversy over the law flared when former information minister Sherry Rehman tabled a bill in November calling to end the death penalty for blasphemy, after Christian mother-of-five Asia Bibi was sentenced to hang.

Rights activists also say the law encourages extremism in a nation already beseiged by Taliban attacks.

Rehman spoke to AFP from her heavily-guarded home in Karachi on Sunday and said she would not be cowed by the protest.

“They can't silence me... it's not any extreme position like a repeal bill, it's very rational. They can't decide what we think or speak, these are man-made laws,” said Rehman.

Politicians and conservative clerics have been at loggerheads over whether President Asif Ali Zardari should pardon Asia Bibi.

Pakistan has yet to execute anyone for blasphemy, but Bibi's case has exposed the deep faultlines in the conservative country.

Christian groups held memorial services in the Punjab cities of Lahore and the capital Islamabad on Sunday to honour the assassinated Muslim governor Taseer.

Bishop Alexander John Malik led a rare gathering of 300 Christians at a cathedral in the eastern city of Lahore.

“He was a voice for the oppressed section of society. We dedicate this day to him,” Malik said, before leading prayers for the governor.– AFP