The flow of foreign fighters to IS in Syria and Iraq has come to a halt, they said, but “the reverse flow, although slower than expected, remains a serious challenge.”

While the rate of terrorist attacks has fallen in Europe, the experts said some governments “assess that the underlying drivers of terrorism are all present and perhaps more acute than ever before.” This suggests that any reduction in attacks is likely to be temporary until IS recovers and reorganizes and al-Qaida “increases its international terrorist activity or other organizations emerge in the terrorist arena,” they said.

The experts looked at the threats posed by IS and al-Qaida by region:

ARABIAN PENINSULA: Al-Qaida’s leaders recognize Yemen “as a venue for guerrilla-style attacks and a hub for regional operations.” Yemen’s lack of a strong central government “has provided a fertile environment for al-Qaida in the Arabian Peninsula.” Its strength inside Yemen is estimated at between 6,000 and 7,000, compared with only 250 to 500 IS members in the conflict-wracked country.

NORTH AFRICA: Despite the loss to IS of the Libyan city of Sirte and continued airstrikes, the extremist group “still has the capacity to launch significant attacks within Libya and across the border, reverting to asymmetric tactics and improvised explosive devises.” Estimates of IS members vary between 3,000 and 4,000, dispersed across Libya. Up to 1,000 fighters in Egypt’s Sinai peninsula have pledged allegiance to IS leader al-Baghdadi. Al-Qaida is also continuing a resurgence in Libya.

WEST AFRICA: An al-Qaida-affiliated coalition has increased attacks on French, U.S., U.N. and other international interests in the Sahel. Al-Qaida in the Islamic Maghreb has urged attacks on French private companies. The Islamic State in the Greater Sahara is active mostly at the Mali-Niger border and has less of a footprint. “Member states assess that terrorists are taking advantage of territorial control and ethnic conflicts to radicalize populations.”

EAST AFRICA: The al-Shabab extremist group in Somalia, an al-Qaida affiliate, “remains the dominant terrorist group” in that country, with improvised explosive devices “its weapon of choice.” Despite sustained military action against al-Shabab, “the group has enhanced its capabilities as it retains its influence and appeal.” Member states said IS in Somalia “is fragile and operationally weak,” but “it still presents a threat” because the country remains a focus for possible future operations.

EUROPE: During the first six months of 2018, “the threat in Europe remained high” but “the tempo of attacks and disrupted plots was lower than during the same period in 2017.” Much activity involved individuals with no prior security records or deemed low risk. IS used the media to urge sympathizers in Europe to conduct attacks in their home countries. Member states expressed concern that returnees could disseminate knowledge and skills related to making drones, explosive devices and car bombs.

CENTRAL AND SOUTH ASIA: According to an unidentified U.N. member state, IS poses an immediate threat in the region but al-Qaida is the “intellectually stronger group” and poses a longer-term threat. Some leaders of the al-Qaida “core,” including al-Zawahiri and Osama bin Laden’s son, Hamza, are reported to be in Afghanistan-Pakistan border areas. IS continues to relocate some key operatives to Afghanistan. One unidentified government reported newly arrived IS fighters from Algeria, France, Russia, Tunisia and central Asian states.

SOUTHEAST ASIA: Despite last year’s heavy losses in the Philippines, IS affiliates in the country “are cash rich and growing in membership.” Intermediaries facilitated financial transfers from the IS “core” to Philippines affiliates and arranged bomb-making and firearms training for recruits from Indonesia at camps in the Philippines. Attacks in Indonesia by an IS-linked network using families as suicide bombers could become “a troubling precedent.”