A pregnant woman was beaten to death by her own family members on the streets of one of Pakistan's most refined cities on Tuesday after marrying against their wishes.

The "honour killing" happened in front of a large crowd of witnesses outside Lahore's grand high court building where Farzana Parveen, 25, had been due to appear in a case brought by her family.

The attack began when one of Parveen's brothers attempted to shoot her before he and other male family members attacked her with bricks and blunt instruments.

Throughout the deadly assault her father simply looked on while no members of the public outside the busy court complex came forward to intervene despite her cries for help.

Some reports said policemen watched the incident – and all of the attackers managed to escape, although her father was arrested.

The affluent city of Lahore likes to think of itself as Pakistan's "cultural capital", far removed from the country's rural hinterland where killings to protect family "honour" are more common.

Parveen and her family come from the small town of Nankana Sahib to the west of Lahore. Her lawyer said her family had been enraged by her decision in January to marry Muhammad Iqbal rather than one of her own cousins, whom they had chosen.

Parveen, who was three months pregnant, was due to appear in the high court in an effort to quash a case brought by her parents, who alleged Iqbal had kidnapped the young woman.

Iqbal said he fell in love with Parveen after the death of his previous wife. He said her family had been angry after failing to extract money from him before their marriage.

"I simply took her to court and registered a marriage," he said, infuriating her family.

According to the women's campaign group the Aurat Foundation about 1,000 Pakistani women are killed every year in "honour killings" committed by their families. Few cases come to court and trials can take years.

Often the killers are allowed to walk free because Pakistan's Islamic-tinged legal system includes concepts that give the right of forgiveness to close relations of murder victims.

Tahira Abdullah, a human rights activist, said it was vital the country follow the civil code rather than sharia law.

"This woman was pregnant so it is a double murder and these murderers must be prosecuted under the criminal laws of Pakistan," she said.

"We are now at a crossroads where we have to decide whether we continue going down the Talibanisation route or whether we go down the rule-of-law route."

But Abid Saqi, a former head of the Lahore high court bar association, said prosecution was still possible, assuming the men were captured and it was proved that her husband was the legal heir.

"This is a tragic and unfortunate event right in front of the doors of justice," he said. "This person was mutilated to bits in public and it shows the complete breakdown of law and order."