The top UN envoy in Afghanistan says recent reports indicate the Islamic State (IS) extremist group has moved into Afghanistan.
Nicholas Haysom was speaking to the UN Security Council on March 16.
He said the UN mission's assessment is that IS has not stuck "firm roots" in Afghanistan.
However, Haysom said IS had the potential "to offer an alternative flagpole to which otherwise isolated insurgent splinter groups can rally."
Haysom's view was echoed by Russia, which urged the Security Council to stop the militant group's expansion.
Russian Deputy UN Ambassador Vladimir Safronkov said Moscow is worried about what he said was an increased terrorist threat in Afghanistan, especially in the formerly quiet north bordering former Soviet republics in Central Asia that he called Russia's friends and allies.
The two were speaking on March 16 at the start of a meeting during which the Security Council voted unanimously to extend the mandate of the UN mission in Afghanistan until March 17, 2016.
Afghanistan's UN Ambassador Zahir Tanin agreed that there are reports of Islamic State militants group penetrating more areas including Afghanistan, "but the main enemy we face is the Taliban that continue to fight against us."
He added that there may also be "some splinter groups with more extreme orientations."
Safronkov said extremists in the north are actively engaging in propaganda activities and recruiting, and were setting up camp.
The resolution adopted by the council calls on the Afghan government, with help from the international community, to continue to tackle threats from the Taliban, Al-Qaeda, other extremist groups, and drug traders. It does not mention the Islamic State militant group by name.
In its resolution extending the UN mission in Afghanistan, the Security Council stressed the importance of an "Afghan led and Afghan-owned" political process to support reconciliation for all those who renounce violence, have no link to terrorist groups, and respect the constitution including the rights of women.
Tanin said the peace and reconciliation process was the government's first priority, especially "when violence affects increasing numbers of civilians and when the crippling triple threat of terrorism, extremism, and criminality threatens to undermine the future of the Afghan people and the wider region."