The remains of a destroyed car at the scene of a suicide attack in Mogadishu, Somalia, on July 31 that was claimed by al-Shabab. (Said Yusuf Warsame/EPA)

Somalia-based al-Shabab militants pose a rising threat to nations across East Africa, which are among the continent’s fastest-growing, according to a report released Monday by a regional bloc of eight countries.

The report by the Intergovernmental Authority on Development notes that al-Shabab, like the Islamic State militant group, has been able to recruit young men and women from countries beyond its power base.

The report also includes new details about terrorists who “exploit weaknesses to operate across the region’s borders.”

Al-Shabab “is clearly no longer an exclusively Somali problem, and requires a concerted international response,” according to the report, titled “Al-Shabab as a Transnational Security Threat.”

The report’s conclusions underscore a shift in assessments about al-Shabab, which has shown resilience in the face of setbacks in recent years. Until recently, the governments of East African nations had played down the regional threat posed by the al-Qaeda affiliate, rarely sharing intelligence or coordinating counterterrorism campaigns.

After emerging in Somalia in 2006, al-Shabab captured a large swath of the country through years of withering guerilla warfare. In recent years, though, many of those territorial gains were lost after a campaign by 22,000 African Union troops and U.S. drone strikes.

Al-Shabab, however, maintained its ability to carry out spectacular attacks inside and outside Somalia. In 2013, fighters attacked an upscale shopping mall in Nairobi, killing 67. In 2015, they attacked a university in northern Kenya, killing 148. Over the past 18 months, al-Shabab has been behind a slew of bombings in Mogadishu, Somalia’s capital, but it has not launched any major attacks elsewhere in the region. That led some to question whether al-Shabab’s regional ambitions or abilities have waned.

The new report suggests that neither is true. It said the group has a presence in five countries: Kenya, Ethiopia, Djibouti, Tanzania and Uganda. It said the group maintains “safe houses” in Kenya “within which they can securely meet, plan, and execute operations. Al-Shabab is also “actively developing new external operations in Ethi­o­pia,” according to the report.

The report said that the group also has maintained its ability to recruit young women, who have previously played key roles in cross-border attacks.

Female couriers, the report says, “routinely travel across East Africa on behalf of Al-Shabab, building and sustaining transnational networks.”

The report recommends identifying “gaps, challenges, and opportunities in strengthening cooperation to combat Al-Shabab.”

But the countries that make up the Intergovernmental Authority on Development have been slow to adapt to the threats posed by the group, and it remains unclear how quickly cooperation on security matters will improve.