Updated

The Islamic State extremist group has reorganized its military structure, giving local commanders more power and inspiring attacks outside conflict areas, the U.N. political chief said Thursday.

Jeffrey Feltman told the U.N. Security Council that the threat from the militant group has intensified because of its use of the internet and social media to disseminate propaganda.

Although the volume of messages from the Islamic State group has declined in the last 16 months, he said, "the threat persists as supporters outside Syria and Iraq collect and redistribute this propaganda."

Feltman said the group — also known as IS or ISIL — has used its online presence to encourage supporters to carry out attacks in Europe including in Belgium, Britain, France, Germany, Russia, Sweden and Turkey.

Some attacks were carried out by fighters returning from Iraq and Syria while others were by people who had not traveled to conflict zones, he said.

"Despite being sometimes labeled as 'lone actors,' investigations demonstrate that the perpetrators often received support or resources from facilitators and, in a number of cases, were in direct contact with ISIL enablers," Feltman said.

Elsewhere in the world, he said IS-affiliated groups in North Africa "pose a serious danger" and IS is challenging established al-Qaida affiliates in West Africa.

He said IS in Somalia and Yemen "represent an increasing menace" and the threat level from IS in Southeast Asia has intensified because the extremist group is now focusing more attention in that region.

Feltman said that while the flow of "foreign terrorist fights" to Syria and Iraq has decreased during the last 16 months, fighters returning home or relocating to other regions "present a considerable threat to international security."

He said the Islamic State group's financial situation has also declined over the last 16 months — but he cautioned that as it loses control of population centers in Iraq and Syria and its forces dwindle, its costs will also be lower.

"Despite liquidity shortages," Feltman said, "ISIL may be able to stretch further its existing resources."

He said ISIL continues to rely on the same two sources of revenue — oil and gas sales "and extortion/taxation, which may amount to tens of millions of dollars per month."

"ISIL has also drawn income from antiquities smuggling, agricultural products, sale of electricity, exploitation of mineral resources such as phosphates and sulfuric acid, external donations, kidnapping for ransom, and human trafficking," Feltman said.