Pakistan's Supreme Court has ordered an investigation into reports that four convicted killers sought to buy their freedom by offering girls in marriage to relatives of their victims.

This is a negation of Islamic law

Zia Ahmad Awan, human rights lawyer

According to local press reports, the four men had been sentenced to hang for murdering two men in the village of Mianwali in Punjab province in 1988.

The killers eventually cut a deal with the families of the victims to give them eight young girls and more than $130,000 in exchange for a pardon.

Three of the girls were less than 10 years old and the age of the youngest was one-and-a-half.

Islamic laws say convicts can be released if families of their victims accept cash compensation, but payment in women is not allowed.

The deal was reportedly cancelled on the advice of local elders and the four men are due to be executed on Saturday.

Secret deals

Pakistan's Chief Justice, Sheikh Riaz Ahmed, was quoted in the Dawn daily as saying the case violated the "law of the land and... the norms of the civilised world".

The country's Human Rights Commission has also sent a task force to Punjab to launch its own investigation.

Although deals involving women are illegal, human rights lawyer Zia Ahmad Awan told the AFP news agency they were still conducted in secret.

"Often money is paid, but under the table there is a payment by way of women and children," said Mr Awan, who heads the Karachi-based Lawyers for Human Rights and Legal Aid.

"This is trafficking in women and children... This is a form of slavery. This is a negation of Islamic law," he was quoted as saying.

A district mayor told the Reuters news agency that teenage daughters of two of the murderers had already married two relatives of the victims - one aged 80 and the other 55.

But he said the men divorced the girls later the same day after local elders said the arrangement was unethical.

A local newspaper reporter, however, said the marriages were called off under police pressure.

Abuse

Women's rights in Pakistan came under international scrutiny earlier this month after a Punjabi woman was gang raped on the orders of a local tribal council.

The gang rape case aroused much anger

The Supreme Court is still investigating the gang rape, ordered because the girl's brother was seen walking unchaperoned with a woman from another tribe.

Following the case, which sparked outrage at home and abroad, Chief Justice Ahmed summoned the police chief of Punjab, along with other senior provincial officials, to appear before the Supreme Court.

The Human Rights Commission has recently published a report saying that rape and "honour killings" have become widespread in southern Punjab.

The report said more than 150 women were sexually assaulted in the first six months of the year in the area.

There were also about 40 so-called "honour killings", carried out by men who allege that the behaviour of a woman has brought dishonour to their family.

But the commission said law enforcement agencies were still treating the perpetrators with leniency.