The alleged honour killing of four sisters in Pakistan has outraged human rights groups in the conservative Islamic country, where such deaths are common.

Nazir Ahmed, a 40-year-old impoverished labourer from a small town in eastern Punjab province, has been charged following the death of his three young daughters aged four, seven, and eight, as well as their 25-year old stepsister. Police believe he slit their throats last Friday to salvage the family's "honour."

The husband of the eldest daughter, Muqadas, had accused her of adultery. However, rights groups that have intervened in the case said Muqadas had fled an abusive relationship.

She was reportedly killed because of the adultery allegations, and the younger children were killed because of fears they would follow in her footsteps.

Ahmed was arrested the day after the deaths and charged with murder. He faces the death penalty if convicted. Police expected to complete their investigation in the next two weeks.

"I thought the younger girls would do what their eldest sister had done, so they should be eliminated," Ahmed told the Associated Press as he was led away in handcuffs. "We are poor people and we have nothing else to protect but our honour."

Every year, hundreds of Pakistani girls and women are murdered by male relatives. Last year, a new law beefed up the sentences for convictions in so-called honour killings. The minimum sentence is now 10 years and the maximum is death by hanging.

The Ministry of Women's Development said it had no reliable figures because honour killings are difficult to track. However, according to the Human Rights Commission of Pakistan, there were 267 in the first 11 months of this year, down from 579 in 2004.

"Women are treated as property and those committing crimes against them do not get punished," said Kamla Hyat, the director of the commission. "The steps taken by our government have made no real difference."

President Gen. Pervez Musharraf, a self-styled moderate Muslim, has been accused of holding back from reforming outdated religious laws that make it difficult to secure convictions in rape cases, acid attacks and other cases of violence against women.

Activists said police were often reluctant to prosecute crimes considered to have stemmed from a family dispute. More than half of the cases that make it to court end with cash settlements paid by relatives to victims' families.