The Ministry of Defence issued an apology today after admitting that a British-run operation had accidentally killed four civilians in Afghanistan.

The civilians, believed to be two women and two children, were killed in an airstrike called by UK forces in the southern part of war-ravaged Helmand province yesterday, the military confirmed.

British troops called for the operation after being caught in a Taleban ambush. Air support directed fire on to the area where the militants appeared to have been operating, but the civilians were unintentionally killed. The injured person was evacuated to the British field hospital at Camp Bastion for medical treatment.

The civilian casualties were found after soldiers went to inspect the area.

"We deeply regret that this incident happened and do everything we can to mitigate this from happening," the MoD spokeswoman said. "This incident is currently under investigation and it would be inappropriate for us to comment."

The tragedy highlights the responsibility on the shoulders of British Forward Air Controllers - the role filled by Prince Harry until his returned from Afghanistan less than two weeks ago.

The incident took place as coalition forces became embroiled in a diplomatic spat with Pakistan over the separate killing of two women and two children in a cross-border missile attack today.

Pakistan lodged a formal protest after the coalition confirmed it had launched a "precision guided" strike across the Afghan border targeting a militant compound in Pakistan, but the missile had had gone astray.

The issue of foreign military intervention in Pakistan is sensitive, with President Pervez Musharraf, a key US ally, saying earlier this year that unauthorised actions would be treated as an invasion.

Major General Athar Abbas, a Pakistan military spokesmen, said that coalition artillery fire destroyed the victims’ house in the tribal region of North Waziristan, an alleged haven for Al-Qaeda and Taliban militants.

"The coalition forces were firing at a group of militants when five shells landed in Pakistan, destroying a house and killing two women and two children," Major General Abbas told the AFP news agency.

"We have lodged a very strong protest with the coalition forces across the border."

A coalition spokesman said it could not comment directly on the Pakistani account but confirmed it had launched a strike on the other side of the porous 1,500-mile frontier.

"We can confirm a precision-guided ammunition strike on March 12 on a compound connected with Haqqani network 1.5km (one mile) across the border in Pakistan," coalition spokesman Major Chris Belcher told AFP.

Meanwhile, Nato this morning reported that Afghan and international forces had killed 41 militants in a battle in the south of the country.

In Kabul, meanwhile, a suicide car bomb attack targeting a convoy of US troops left six Afghan civilians dead. None of the four American troops in the convoy were wounded.

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