The Taliban's increasing use of homemade bombs and political assassinations has caused the number of civilians killed or injured in fighting in Afghanistan to rise by nearly a third this year (31%), the United Nations said today.

The UN's Kabul mission released data showing that, even as the number of child casualties has soared by 55%, strict rules on the use of air power by Nato troops has led to a 30% drop in deaths and injuries caused by foreign forces in the first six months of this year, compared to the same period in 2009.

Today also saw a double suicide attack on a western security company in a neighbourhood of Kabul that, despite being home to many foreign organisations, has not been targeted in the past.

UN human rights workers recorded 1,271 civilians deaths over the period and 1,997 injuries. Of that total of 3,268, insurgent forces were responsible for 2,477 casualties, while Nato and Afghan government forces accounted for 386.

The research highlights the remarkable turnaround achieved under Stanley McChrystal, the disgraced former US commander of all Nato forces in Afghanistan, who made protecting Afghan civilians a top priority even at the cost of putting his troops at greater risk by restricting their freedom to use heavy weapons.

The report said a 64% drop in the use of "aerial attacks" by the coalition and been largely responsible for the 30% decrease in casualties caused by Nato.

Despite political pressure on David Petraeus, McChrystal's successor, to loosen the rules, the new commander of Nato in Afghanistan has largely recommitted the coalition to avoiding civilian casualties as much as possible.

"Every Afghan death diminishes our cause," Petraeus said in a recently published tactical directive.

"While we have made progress in our efforts to reduce coalition-caused civilian casualties, we know the measure by which our mission will be judged is protecting the population from harm by either side."

But despite the efforts of foreign forces to wage a "population-centric" counter-insurgency campaign, the report criticised the two main Nato operations of the year. It said that large-scale military operations, such as the Operation Moshtarak in Helmand at the beginning of the year, "remain deeply unpopular" with local communities because "they are believed to result in further insecurity and less protection for the area and its inhabitants".

It also criticised the ongoing push to bring greater security to Kandahar city and its surrounding areas, saying the pre-publicity for the operation only increased Taliban activity.

Staffan de Mistura, the UN chief in Afghanistan, said women and children were "increasingly bearing the brunt of this conflict".

"They are being killed and injured in their homes and communities in greater numbers than ever before," added de Mistura.

Driving the overall increase in civilian casualties caused by insurgents is the use of larger and more sophisticated bombs which are typically buried in roadsides and tracks to target Nato convoys and foot patrols. However, they also frequently kill and maim civilians, including a case last month where the Taliban were blamed for planting a bomb that destroyed a bus travelling along a desert highway in southern Afghanistan, killing 25 people.

The number of children killed by improvised explosive devices rose 55% the report said.

The other factor has been the near doubling of the Taliban's use of assassinations to dissuade Afghans from working for the government or its international backers or its international backers.

The report said that whereas assassinations averaged 3.6 a week last year, they are now running at one a day. In May and June they "skyrocketed" to an average 18 per week, the report said. Teachers, doctors, tribal elders, community leaders, provincial and district officials have all been targeted.

"This intensified pattern of assassinations and executions reinforced the widespread perception of Afghan civilians that they are becoming more and more the primary target in this period of conflict," de Mistura said.

The United Nations called for the Taliban to withdraw "all orders and statements calling for the killing of civilians", stop roadside bomb and suicide attacks, and cease acts of intimidation and the use of civilians as human shields.

This afternoon in Kabul two suicide bombers shot at guards before blowing themselves up outside the compound of a security company, in a quiet street in a part of the capital that has not seen insurgent attacks before. Two Afghan staff working for Hart security were killed and another injured.