"The human cost of this conflict is unfortunately rising," Staffan De Mistura, the UN special envoy in Afghanistan said while releasing the report.

"We are concerned. We are very concerned about the future because the human cost is being paid too heavily by civilians. This report is a wake-up call."

According to the report, the previously more stable northeastern region has seen a sharp increase in anti-government activities, with the death toll in that area increasing by 136 per cent.

The surge in Nato's International Security Assistance Force (Isaf) supported operations have intensified the conflict, raising the civilian toll around Kandahar city and surrounding areas in southern Afghanistan.

'Enormous responsibility'

De Mistura emphasized that both the Afghan government and its international allies bear "enormous responsibility" to protect non-combatants.

General David Petraeus, the head of US and Nato forces in Afghanistan, issued new rules to troops in Afghanistan earlier this month, asking them to "redouble" efforts to avoid civilian deaths.

Petraeus said he believed the counter-insurgency strategy was bearing fruit but warned that any civilian casualties risked losing the battle to win Afghan hearts and minds.

"We must continue - indeed, redouble - our efforts to reduce the loss of innocent civilian life to an absolute minimum. Every Afghan civilian death diminishes our cause."

On his part, Hamid Karzai, the president of Afghanistan, has repeatedly pleaded with troops to "employ necessary precautions to avoid [civilian death] and make this a top priority in operations".

Leaked documents from US military field reports revealed by the whistleblowers website Wikileaksearly this month have showed that the US military attempted to cover up civilian casualties in Afghanistan, raising questions about the number of casualties reported.