Ground combat is now causing more deaths and injuries than improvised explosive devices (IEDs) in a worrying sign of spreading conflict, the UN report said, with women and children increasingly caught in the crossfire.
"The nature of the conflict in Afghanistan is changing in 2014 with an escalation of ground engagements in civilian-populated areas," warned Jan Kubis, the United Nations mission chief in Afghanistan.
In the first six months of this year, UNAMA documented 4,853 civilian casualties -- up 24 per cent over the same period in 2013.
The toll included 1,564 deaths and 3,289 injuries, with ground engagements causing two out of every five civilian casualties in 2014.
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The grim figures underline the fragile security situation Afghanistan faces as it wrestles with political turmoil over its disputed presidential election.
One candidate, Abdullah Abdullah, has refused to accept the result and fears are growing of ethnic tension and clashes between rival supporters.
With NATO troops pulling out, the coming months are expected to be a test of the fledgling Afghan government forces, trained by the US-led military coalition since the Taliban were ousted in 2001.
"The fight is increasingly taking place in communities, public places and near the homes of ordinary Afghans, with death and injury to women and children in a continued disturbing upward spiral," said Georgette Gagnon, director of human rights for UNAMA.
The ICG concluded that "the overall trend is one of escalating violence and insurgent attacks" in Afghanistan, with insurgents now able to mass in larger numbers and trying to capture rural territory and district administration centres.