A gang in north Afghanistan reportedly indignant at a father's refusal to give his daughter up for marriage have sprayed the family of five with acid.

Allegedly led by the suitor, they broke into the house in Kunduz, beat the father up, then sprayed him, his wife and three daughters in the face.

The father and eldest daughter are in critical condition, doctors say.

The lives of the wife and other two daughters are said to be out of danger after the attack early on Wednesday.

Skin-burning acid is used intermittently as a weapon in Afghanistan, usually against women, correspondents say.

Family members told the BBC the trouble had stemmed from the father's refusal to allow a member of a militia known as the Arbakis to marry the elder daughter, Mumtaz, 18.

The suitor was reportedly much older than the young woman.

He allegedly broke into the family home with his followers carrying acid in buckets.

Growing problem

"The man who did this is a criminal thug," a family member told the BBC's Bilal Sarwary in Kabul.

"There is no reason why we should be forced to accede to his demands. It is now a serious crime he has committed and the police must arrest him.''

The Arbakis have been accused of a range of crimes including rape and extortion, our correspondent says.

Many people in Kunduz believe police will not pursue them because they have been fighting the Taliban and are considered a powerful force but police told the BBC that there were no Arbakis in Kunduz.

However, no-one denies that acid attacks are a growing problem.

In the conservative, Taliban-influenced south and east, acid has been thrown at girls attending schools.

In January, veteran Afghan journalist Abdul Razaq Mamon was left with burns to his hands and face after acid was thrown at him in Kabul.