Nearly 80 Afghan police have died every week during the current fighting season, officials said Tuesday, as the national security forces take on the battle against Taliban militants.

The figures, which are in addition to Afghan soldiers killed, reflect a sharp rise in casualties at a time when US-led NATO forces are stepping back from the frontline and steadily withdrawing 87,000 troops by the end of next year.

Afghanistan's fighting season traditionally begins in April or May as snow melts in mountains, and slows in November, when winter sets in.

This year the Taliban launched their annual offensive six months ago on April 27, vowing a nationwide series of multiple suicide bombings, "insider attacks" and roadside bombings.

"Since the Taliban launched their operation, they have conducted 6,604 operations, 50 suicide attacks and 1,704 direct attacks on police," General Salim Ehsas, deputy interior minister, told a conference in Kabul.

"1,273 national police, 779 local police, and 858 civilians have lost their lives."

Around 5,500 police and civilians were wounded in attacks, he said, adding that most Taliban operations were in provinces such as Logar and Ghazni, close to the capital Kabul.

The defence ministry and military have declined to release Afghan army casualty figures this year, but admit that levels have climbed.

In June, Afghan forces took control of security across the country, marking a major milestone as US-led combat troops prepare to end more than a decade of war.

This year's "fighting season" has been seen as crucial to Afghanistan's future, as its much-criticised security forces pitted themselves against the insurgents who have waged a guerrilla war against the Kabul government since 2001.

"The year that passed was a very difficult one... and it was a very dangerous one," defence ministry spokesman General Zahir Azimi said.

"They wanted to show that Afghan security forces are not able to provide security for the country, but our army, police and other security forces neutralised their plans."

Doubts remain over the ability of Afghan forces to thwart the Taliban, and the NATO military coalition retain an important function in logistics and air support as well as in combat emergencies.