Self-described Taliban gunmen have shot dead Pakistan's minorities minister, Shahbaz Bhatti, an advocate of reform of the country's blasphemy laws, as he left his Islamabad home.

Two assassins sprayed the Christian minister's car with gunfire, striking him at least eight times, before scattering pamphlets that described him as a "Christian infidel". The leaflets were signed "Taliban al-Qaida Punjab".

Bhatti's 22-year-old niece Mariam was first on the scene. "I rushed out to find his body covered with blood. I said "uncle, uncle" and tried to take his pulse. But he was already dead," she said at Bhatti's house, extending a bloodstained palm. The sound of wailing women rose from the next room.

Pakistan's prime minister, Yusuf Raza Gilani, consoles relatives of Shahbaz Bhatti, the slain minister for minorities. Photograph: Faisal Mahmood/Reuters

Bhatti's assassination was the second killing of a politician in Islamabad over blasphemy in as many months, following the assassination of the Punjab governor Salmaan Taseer outside a cafe a few miles away on 4 January.

Dismayed human rights activists said it was another sign of rising intolerance at hands of violent extremists. "I am sad and upset but not surprised," said the veteran campaigner Tahira Abdullah outside Bhatti's house. "These people have a long list of targets, and we are all on it. It's not a matter of if, but when."

The only Christian in Pakistan's cabinet, Bhatti had predicted his own death. In a farewell statement recorded four months ago, to be broadcast in the event of his death, he spoke of threats from the Taliban and al-Qaida.

But he vowed not to stop speaking for marginalised Christians and other minorities. "I will die to defend their rights," he said on the tape released to the BBC and al-Jazeera. "These threats and these warnings cannot change my opinions and principles."

Lax security did not help. Witnesses and police said Bhatti was travelling with just his driver when he came under attack less than 50 metres from the Islamabad home he shares with his mother.

A small white car carrying gunmen blocked his way. After an initial burst of fire they dragged Bhatti's driver from the vehicle, then continued firing through a side window. "It lasted about twenty seconds," said a neighbour, Naseem Javed. "When I rushed out I saw the minister's driver standing by the car, shivering, and his niece weeping and shouting."

"They fired 25 bullets," said a police officer beside a bullet-pocked pavement, holding a handful of brass Kalashnikov bullet cases.

As they left the gunmen flung pamphlets on to the road that blamed President Asif Ali Zardari's government for putting an "infidel Christian" in charge of a committee to review the blasphemy laws. The government insists no such committee exists. "With the blessing of Allah, the mujahideen will send each of you to hell," said the note.

Last November Bhatti joined Salmaan Taseer in championing the case of Aasia Bibi, a Christian woman who was sentenced to death last November for allegedly committing blasphemy against the prophet Muhammad.

"This law is being misused," Bhatti told Open magazine at the time. "Many people are facing death threats and problems. They're in prison and are being killed extra-judicially."

The government later distanced itself from the blasphemy reformists, repeatedly stressing that it had no intention of amending the law, leaving Bhatti and Taseer politically isolated. Now that both men are dead, angry supporters say the government bears some responsibility for not protecting them politically, if not physically.

"The government distanced itself from anyone who took a stand on blasphemy. I blame them for being such chickens," said Abdullah.

Ali Dayan Hasan of Human Rights Watch said Bhatti's death represented "the bitter fruit of appeasement of extremist and militant groups both prior to and after the killing of Salmaan Taseer".

The embattled Christian community also voiced concerns about its safety. "We feel very insecure," said Bhatti's brother in law, Yousaf Nishan. "In this society you can't open your mouth, even if you want to say something good, because you're afraid who you might offend."

The assassination raised fresh questions about the safety of Sherry Rehman, a parliamentarian who also championed reform of the blasphemy laws, and who has been in semi-hiding since January.

She was not available for comment. Friends said she may have gone into hiding again, fearing for her safety.