Pakistan has hanged the former police bodyguard who shot dead Punjab's governor over his opposition to blasphemy laws, officials say.

Mumtaz Qadri killed Salman Taseer in Islamabad in 2011, a high profile murder that shocked the country.

He was hailed as a hero by some Islamist groups, and thousands of hard-line activists protested to show their support for Qadri at the time.

After news of his execution, crowds again took to the streets in protest.

Security forces have been put on high alert and a heavy police presence, including riot police, are in place in the area around Qadri's home in Islamabad, the AFP news agency reports.

Prison officials said Qadri was executed at 04:30 local time (23:30 GMT) at Adiala jail in Rawalpindi, near the capital, Islamabad.

'Religious duty'

Qadri, who had trained as an elite police commando and was assigned to Taseer as his bodyguard, shot the politician in broad daylight at an Islamabad market in January 2011. He was sentenced to death later that year.

He claimed it was his religious duty to kill the minister, who was an outspoken critic of Pakistan's harsh blasphemy laws and supported liberal reforms.

Pakistan has seen Islamist groups grow in influence in recent years and several high profile blasphemy cases.

Qadri was lauded by religious conservatives, and in his first court appearance was showered with rose petals by supporters. He never expressed any regret for the killing. His brother appeared to reassert that when he told the AFP news agency about his final meeting with Qadri.

"I have no regrets," Malik Abid told AFP. "We started crying, but he hugged us and chanted 'God is great,'" he added.

In May, just months after Taseer was gunned down, Pakistan's Minorities Minister Shahbaz Bhatti, the cabinet's only Christian, was shot dead by gunmen who ambushed his car.

That August, Salman Taseer's son, Shahbaz Taseer, was abducted in Lahore. His whereabouts are still unclear.

Blasphemy is an extremely sensitive issue in Pakistan and critics argue that blasphemy laws are often misused to settle personal scores and unfairly target minorities.