A US-based human rights group on Wednesday demanded the immediate release of Afghan women imprisoned for running away from home, welcoming promises from government officials to stop the detentions.

Up to 70 percent of the estimated 700 women and girls detained in Afghan prisons are being held for running away, nearly always for fleeing forced marriage or domestic violence, according to Human Rights Watch (HRW).

At a meeting last Sunday, Justice Minister Habibullah Ghalib, Women's Affairs Minister Hassan Banoo Ghazanfar and the deputy interior minister, Baz Mohammad Yarmand, condemned wrongful imprisonment of women and girls for leaving their homes.

Afghanistan is an extremely conservative country, where unmarried girls are often confined to the home and forbidden from having any contact with men outside the immediate family.

"The public pledges by top Afghan government officials to end wrongful imprisonment of women and girls fleeing abuse sends an important message of equal rights for women," said Brad Adams, Asia director at HRW.

"Now the onus is on President (Hamid) Karzai and his government to promptly free the women and girls who have lost months or years of their lives on these bogus charges," he added.

Around 50 percent of women and 95 percent of girls in detention are accused of so-called moral crimes, according to HRW research.

Under the constitution, running away is not considered a criminal offence but judges in Afghanistan have classified it as a crime, based on their interpretation of sharia law.

Police arrest girls and women who run away, usually on the recommendation of their fathers, brothers or husbands who typically accuse them of both running off and having sex outside marriage.

"President Karzai should immediately issue a decree prohibiting all arrests and prosecutions for ?running away' and order the release of all women and girls currently imprisoned on this charge," said Adams.

The rights organisation also urged the government to do more to support 14 shelters, which provide the only refuge for women and girls leaving prison who are at risk of being killed by relatives for allegedly defaming the family.

Although significant progress has been made on women's rights since a US-led invasion brought down the Taliban, many fear those gains are under threat as NATO troops leave and Kabul seeks peace with Islamist insurgents.