KABUL, Afghanistan - The U.S.-led international forces in Afghanistan suffered the lowest number of casualties in the past six years in 2013, but Afghan security forces saw their casualties mount as they took the lead in the 12-year war against the Taliban.

The figures underline the dangers this nation still faces as the NATO-led mission nears its end in Afghanistan in 2014.

According to an Associated Press tally, NATO casualties fell to 151 in 2013, down from 394 a year earlier. The U.S. bore the brunt of these attacks, with 118 deaths, down from 297 in 2012.

However, foreign troops still are targeted by insurgents. Just last week, a suicide bomber struck a convoy in the capital, Kabul, killing three NATO troops, including one American.

Casualties among the Afghan army and police rose to 2,767, up from 1,870 the year before. In June, the Afghan army and police took over control of the country's security from the NATO-led International Security Assistance Force, resulting in greater combat losses with the insurgents.

Meanwhile Afghan civilians continued to bear the worst of the war's violence, with the United Nations recording 2,730 deaths and 5,169 wounded through the end of November, a 10 percent increase on a year earlier.

One significant change this year was a steep drop in the number of insider attacks, the so-called "green-on-blue" incidents in which Afghan security turn on their NATO partners. Last year, attacks like this killed 53 coalition troops in 38 separate incidents. In 2013, there were 16 deaths in 10 separate insider attacks.

Maj. Gen. Joseph Osterman, director of operations for the coalition, said most of the credit for the lower insider attacks should go to the Afghan security forces.

"They put in much more robust screening processes, education processes, and at the local level, just awareness of soldiers who were potential `green-on-blue' perpetrators," Osterman said.

The Defense Department says a total of 1,788 Americans have been killed in action in Afghanistan since the U.S. invasion in 2001 through Dec. 30. Some 19,541 have been wounded.