Israr Ullah Zehri, who represents Baluchistan province, told a stunned parliament that northwestern tribesman had done nothing wrong in first shooting the women and then dumping them in a ditch.

"These are centuries-old traditions, and I will continue to defend them," he said.

"Only those who indulge in immoral acts should be afraid."

The women, three of whom were teenagers and whose "crime" was that they wished to choose who to marry, were still breathing as mud and stones were shovelled over their bodies, according to Human Rights Watch.

The three girls, thought to be aged between 16 and 18, were kidnapped by a group of men from their Umrani tribe and murdered in Baba Kot, a remote village in Jafferabad district.

According to some reports, Baluchistan government vehicles were used to abduct the girls, and the killing was overseen by a tribal chief who is the brother of a provincial minister from the ruling Pakistan People's Party.

Some accounts said that two older relatives had tried to intervene, but they too were shot and buried alive with the teenagers.

More than six weeks after the deaths no one has been arrested and human rights groups have accused local authorities of trying to cover up the executions.

Mr Zehri told parliament that a fuss should not be made over the killings, however several politicians stood up in protest, describing the so-called honour killings as "barbaric".

Human Rights Watch described the murders as a "heinous criminal offence".

The Pakistani Daily News condemned the killings and called for those responsible to be brought to justice.

"Surely the government should be seeking the murderers, not protect (them) through some dark conspiracy of silence. The fact the act was 'kept quiet' means the government sympathises with such doings," an editorial said.