AFP/Karachi

Pakistan's Supreme Court Wednesday upheld the death sentence for the killer of a politician who sought blasphemy law reform, in a verdict hailed by moderates as a blow against religious extremism.

Mumtaz Qadri, a former police bodyguard, was feted as a hero by extremist supporters after he gunned down the liberal governor of Punjab province, Salmaan Taseer, in 2011.

Qadri shot Taseer 28 times during broad daylight in an upscale market in the capital Islamabad.

He later admitted the killing, saying he objected to the politician's calls to reform Pakistan's controversial blasphemy laws, which rights groups say are frequently used to carry out vendettas -- particularly against religious minorities.

Taseer had also been vocal in his support of Asia Bibi, a Christian woman who has been on death row since 2010 after being found guilty of insulting the Prophet.

"The criminal application filed by the convict is dismissed and the criminal appeal filed by the state is allowed, the conviction and sentence allowed by the trial court are restored," Justice Asif Saeed Khosa, head of a three-member Supreme Court bench hearing appeals, said.

The court also restored Qadri's terrorism conviction, removed by a lower court in March.

Qadri may now file a review petition against the top court's verdict or appeal to the president for mercy, lawyer Muhammad Amir Malik, who was present at the hearing, told AFP.

"This judgement has also closed for him the option of seeking forgiveness from the family of the deceased because the restoration of the terrorism conviction means that the state will itself become a party against the convict," he added.

During the hearings, Qadri's lawyers drew on Islamic texts to argue that he was justified in killing Taseer, saying that by criticising the law the politician was himself guilty of blaspheming -- an argument rejected by the lead judge.

- Breakthrough verdict -

Blasphemy is a hugely sensitive issue in Pakistan, an Islamic republic of some 200 million, and Qadri has been hailed as a hero by many conservatives eager to drown out any calls to soften the legislation.

At his original trial, Qadri was showered with rose petals by some lawyers. His legal team included two judges, including the former chief justice of Lahore High Court.

Critics including European governments say Pakistan's blasphemy laws are largely misused, with hundreds of people languishing in jails under false charges.

Even unproven allegations frequently stir mob violence and lynchings, as in the case of a Christian labourer and his wife who were burned alive on a brick kiln stove last November.

Abbas Nasir, the former editor of leading English-daily Dawn, said Wednesday's verdict was a breakthrough for the country's judiciary, who have in the past been accused of allowing their personal religious sentiments to affect their rulings.

"It does show the coming of age of the judiciary. The country's highest court has spoken through its verdict rather than via the politics of the judges," he told AFP.

- Backlash? -

The ruling was hailed by Pakistani liberals, but could yet stir controversy and protests among supporters of Qadri.

When the Islamabad High Court upheld his death sentence in March, around 150 conservative activists rallied outside the court carrying flags and portraits of him.

Police this week stopped dozens of Qadri supporters from entering the high-security Red Zone of Islamabad, where the Supreme Court and other key government buildings are located.

Moderates voiced their optimism over Wednesday's ruling, however.

"Suspend your cynicism. Pakistan is changing. Still some way to go. Too much past baggage. But a path is taken. And it's the correct one," Nadeem Paracha, a social commentator, tweeted after the verdict.

"JUSTICE... finally!!" tweeted Aamna Taseer, the politician's widow.

Pakistan lifted a moratorium on executions in December after Taliban gunmen massacred more than 150 people at a school, at first only in terror-related offences, but later for all capital cases.

It also instituted a grand National Action Plan to counter terrorism, which has seen the state crack down on militant groups it previously tolerated and jail preachers convicted for hate speech.

Around 200 people have been executed since the moratorium was lifted, and no mercy petitions to the president have been accepted.