A roadside bomb has torn through a minibus carrying people to a wedding celebration in northern Afghanistan, killing at least 19 people and wounding 16, authorities said.

Bismullah Muslimyar, the district police commander who gave the death toll, said six children and seven women were among those killed in Balkh province on Friday morning. He said a police patrol had passed through Dawlat Abad district attack site during the night.

From the perspective of one neighbourhood in Herat

"All the victims were civilians and mostly they were women and children," Shir Jan Durrani,  provincial police spokesman, told the AFP news agency.

The bus was taking guests to a wedding celebration in the Dawlat Abad district, about 40 kilometres from provincial capital Mazar-e-Sharif, Durrani said

Muslimyar said the wedding had occurred Thursday, and the party was heading to the groom's home to congratulate the newlyweds according to tradition.

Hamid Karzai, the Afghan president, strongly condemned the attack.

“Planting a mine on a road used by civilians and the killing of innocent people represents hostility toward humanity,'' he said in a statement.

There was no immediate claim of responsibility for the attack.

Earlier this month, the United Nations Security Council expressed serious concern at the high number of civilian casualties in the war, especially among women and children.

Women and children accounted for about 30 per cent of this year's casualties, mostly victims of roadside bombs.

The Taliban and other armed groups are responsible for the overwhelming majority of civilian deaths in the country. About 77 per cent of the deaths between January and June can be attributed to fighters, a UN report said.

Homemade bombs continue to be the deadliest weapon for civilians, accounting for 29 per cent of all such deaths in the period, it said.

Free and fair elections

Meanwhile, NATO's visiting top official urged the Afghan government to ensure that the next presidential elections in 2014 are free and fair. Karzai will not be able to run after having served the maximum two terms in office.

“It's essential for the trust between the Afghan people and government that these elections take place in a free, transparent and inclusive manner,'' Anders Fogh Rasmussen, NATO secretary-general said in Mazar-eSharif where he and envoys from NATO's governing body were concluding a two-day visit to Afghanistan.

There is mounting uncertainty about the upcoming transfer of power, which will come as NATO's troops prepare to end their combat role at the end of 2014.