"ISIL-K has improved its financial and logistical capabilities in the past six months, including by tapping into Afghan and Central Asian diasporas for support," Vladimir Voronkov, undersecretary-general for counter-terrorism, said.
ISIL-K, or ISIS-K, is an acronym of the jihadist group's branch in Afghanistan, known as Islamic State Khorasan Province.
The group claimed a March attack on a music hall in Moscow, which left 145 people dead.
On Wednesday, Austrian authorities detained Islamic State-linked suspects for allegedly plotting to attack a Taylor Swift concert in Vienna, though no link has been reported to the Afghanistan branch.
But the risk of the Afghanistan branch carrying out terrorist attacks abroad has "become manifest," Voronkov said, noting the group has also intensified its recruitment efforts.
In the latest report from UN Secretary-General Antonio Guterres on the subject, published last month, it was noted that authorities were on high alert against potential attacks during the Euro football championship and Paris Olympics.
"I call on all member states to unite to prevent Afghanistan from again becoming a hotbed of terrorist activities that affect other countries," Guterres wrote.
Elsewhere, Voronkov warned of resurgence of Islamic State's core structure in the Middle East, as well as a deteriorating situation in Africa, where Islamic State West Africa Province and Islamic State's Sahel branch "have expanded and consolidated their areas of operations."
"Should these groups extend their influence... a vast territory stretching from Mali to northern Nigeria could fall under their effective control," he said, while also noting increasing attacks by Islamic State affiliates in Mozambique, Democratic Republic of the Congo and Somalia.