The US defence secretary has warned of a threat from the Islamic State of Iraq and the Levant (ISIL) group in Afghanistan during an unannounced visit.
Ashton Carter's visit comes just days after the Pentagon said, in a report to the US Congress, that there was a 27 percent increase in high-profile attacks in Kabul from January to mid-November this year, compared with the same period in 2014.
"We are seeing little nests of ISIL spring up around the world, including here in Afghanistan, but I will say that that is a threat that we track very closely," Carter said after meeting Masoom Stanekzai, the acting Afghan defence minister, in Kabul on Friday.
"The Taliban's advances in some parts of the country, even if only temporary, underscore that this is a tough fight and it's far from over."
The Pentagon report said Afghan national defence and security forces had 27 percent more casualties from the beginning of 2015 up to mid-November compared with the same period last year.
Meanwhile, US Army General John Campbell, who leads international forces in Afghanistan, said ISIL had coalesced over the last six months in Nangarhar and Kunar provinces.
Between 1,000 and 3,000 ISIL fighters are in Afghanistan, according to Campbell.
He said their presence had forced the Taliban to re-direct some resources away from fighting Afghan security forces.
"It [ISIL] doesn't have the capability, I believe, to go to Europe and attack Europe and go to our homeland at this point," Campbell said.
He said Afghan forces had shown resilience during a "very tough year" but would need assistance for some time.
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"I do believe Afghanistan will continue to need our support and the international community's support," Campbell said.
ISIL has seized large expanses of territory in Iraq and Syria and in recent months mounted attacks on Afghan security forces in Nangarhar.
In mid-October, President Barack Obama announced that the US would extend its military role in the country and keep the current force of 9,800 troops through most of 2016.
Under the new plan, the number would fall to 5,500 the following year.