Afghan security forces have lost control over a small percentage of the terrain they previously held, but are getting better at repelling the Taliban overall, a top US general said Friday.

Kabul now directly controls about 64 percent of the country's population of 30 million, General John Nicholson, the chief US and NATO commander in Afghanistan, said -- down slightly from 68 percent he cited earlier this year.

The Afghans now no longer under government control are not in the hands of the Taliban, but live in areas that are being "contested," he said.

"While the enemy controls slightly more terrain than before, they do not control more of the population than they did in April," Nicholson said.

All told, Kabul still directly controls about two-thirds of the population.

"The enemy holds less than 10 percent, and the balance is contested," Nicholson said.

Afghan police and army units took over providing security for Afghanistan from NATO in 2015.

Their first year was something of a disaster, when they sustained more than 5,000 fatalities and saw the regional capital Kunduz briefly captured by the Taliban.

Despite tracking even higher casualty numbers so far this year, Nicholson said the Afghans had inflicted a high death toll on the Taliban and are improving, having prevented eight Taliban attempts to seize another regional capital.

"Every one of these attempts failed," he said.

"This is a sign of an army that's growing in capability, that's maturing in terms of its ability to handle (simultaneous attacks) and complexity on the battlefield."

The Taliban have been especially active in Helmand province -- a global center for opium production -- and are working with traffickers, Nicholson said.

"There's a nexus here between the insurgency and criminal networks that's occurring in Helmand that makes Helmand such a difficult fight," he added.

Nicholson also blasted the "malign influence" of "external actors," including Pakistan, Russia and Iran, which he said enabled or legitimized insurgent groups inside Afghanistan.