The increase reverses a decline in 2012 and raises questions about how Afghan government troops can protect civilians as US-led NATO troops withdraw from the 12-year war against the Taliban.

The UN Assistance Mission in Afghanistan (UNAMA) said 1,319 civilians died and 2,533 were injured as a result of the war from January 1 to June 30, up 23 percent on the same period in 2012.

UNAMA said there was a 14 percent increase in total civilian deaths and a 28 percent increase in total civilian injuries.

Female civilian casualties rose 61 percent, most caused by fighting on the ground between pro-government and insurgent forces, the UN said in a report.

Child casualties were up 30 percent with improvised explosive devices (IEDs), the Taliban weapon of choice, the leading cause.

"The rise in civilian casualties in the first half of 2013 reverses the decline recorded in 2012, and marks a return to the high numbers of civilian deaths and injuries documented in 2011," the report said.

The UN said 74 percent of the casualties were caused by insurgents, nine percent by pro-government forces and 12 percent as a result of ground fighting between the two sides.

The remaining four or five percent of civilian casualties were unattributed, caused mainly by explosive remnants of war, it added.

While IED attacks remain the highest cause of civilian casualties, increased ground fighting between Afghan troops and insurgents was the second leading cause and a new trend in the first half of 2013.

The NATO combat mission is due to close down at the end of 2014 and Afghan government forces have taken the lead in the battle against the Taliban, who were deposed in the 2001 US-led invasion.

"Despite Afghan forces leading almost all military operations countrywide, a permanent structure does not exist... to systematically investigate allegations of civilian casualties, initiate remedial measures and take follow-up action," the UN said.

The UN also recorded a 76 percent increase in civilian casualties as a result of insurgents targeting civilian government employees, government offices, district headquarters and other offices.

There was no immediate reaction from either the Afghan government or the Taliban, which usually deny targeting civilians.

The UN report also recorded a sharp decline of 30 percent in the number of civilian casualties as a result of NATO air strikes, which in the past have been a source of considerable controversy.

The International Security Assistance Force in Afghanistan welcomed the report and blamed the Taliban for nearly 90 percent of civilian casualties.