(CNN) -- Five people arrested in the public stoning death of a pregnant Pakistani woman will be taken to an anti-terrorism court, authorities said.
Farzana Parveen, 25, was killed in Lahore because she married a man against her family's wishes.
Police arrested her father, her uncle, two cousins and the driver who brought them to Lahore, said Zulfikar Hameed, the lead investigator in the case.
The court is treating the act as an act of terror that has "wider consequences on the safety and well being of all of society," according to lawyer Maliha Zia, who works for Aurat Foundation, a Pakistani women's rights organization.
She said she was worried that international pressure may have forced the government to convene an anti-terrorist court in an act of "show and tell."
"I hope that the quality of the trial does not go down if it's sped up," she said. "The investigation does not suffer and the trial does not suffer because of the shortened time period. What I'm hoping for is a better quality trial."
Pakistani police officers will be investigated because they didn't intervene when Parveen was publicly beaten to death with bricks, a court official said.
Prime Minister Nawaz Sharif on Friday called the killing "totally unacceptable" and said it's a "great shame" for such a crime to happen in the presence of police.
About 20 people, including members of Parveen's immediate family, attacked her with bricks Tuesday outside a court building in Lahore, police said.
Such killings not uncommon
Such killings often originate from tribal traditions in Pakistan but are not a part of Islam. They usually happen in rural areas, not large cities such as Lahore. Human rights activists said bystanders, including police, often don't intervene because the killings are considered family matters.
The Human Rights Commission of Pakistan said 869 women were victims last year (PDF) in the nation of about 180 million people.
They are sometimes called honor killings because the women are accused of bringing dishonor upon the family by having an adulterous affair, being raped or wearing clothes considered revealing.
Women's rights advocates say the actual number may be much higher. The United Nations estimates that at least 5,000 women worldwide die yearly in such killings.
The prevalence of violence against women in Pakistan became apparent Thursday when Parveen's husband, Mohammad Iqbal, revealed to CNN that he killed his first wife six years ago so he could marry Parveen. His son said Iqbal served a year in jail.
Iqbal, a neighbor of Parveen's family, said he and Parveen were supposed to marry with the family's approval last year. In December, her father and brothers decided Parveen, who came from a village in Punjab, should instead marry a cousin, police said.
Bride's family infuriated
Parveen and Iqbal eloped and were married January 7 in a court ceremony. But Iqbal told GEO TV that Parveen's family was infuriated and filed a kidnapping case against him and other members of his family. They also demanded 100,000 rupees (about $1,000), he said.
The couple went into hiding and filed statements in court to prove the kidnapping allegations false, Iqbal said. On Tuesday morning, they were scheduled to appear before a judge when Parveen's family allegedly attacked outside the court building.
"We went to the court to seek justice to tell them what had happened. We were sitting there when all of a sudden they appeared," he told GEO TV. "Someone fired shots in the air. My wife and I were sitting, and then bricks were thrown. Then a lady came and took Farzana away."
Police stood and watched and didn't come to their aid, Iqbal said. He said the crowd killed his wife and her fetus.
In addition to the prime minister, other officials rushed to denounce the killing.
The chief minister of Punjab, Shahbaz Sharif, gave a 24-hour ultimatum to the inspector general to arrest the suspects. He asked that a murder trial be held in an anti-terrorism court.
Britsh Foreign Secretary William Hague said, "There is absolutely no honor in honor killings, and I urge the government of Pakistan to do all in its power to eradicate this barbaric practice."
CNN's Sophia Saifi reported from Islamabad. CNN's Aliza Kassim reported and wrote in Atlanta, and Ralph Ellis wrote in Atlanta.