The Somali-based terrorist group that claimed responsibility Monday for twin Ugandan bombings has rapidly climbed toward the top of al Qaeda-linked organizations that threaten U.S. security, officials and counter terrorism experts said.

Al Shabaab, which has sent fighters to Afghanistan and Iraq, said it planted the bombs that killed 74 people watching the World Cup final. The attacks came two days after threats from the group that “we will attack enemies wherever they are.”

American anti-terror experts are taking that threat seriously, citing the organization’s ability to recruit new members in the United States over the past year, a U.S. counterterrorism official told The Washington Examiner.

“Al Shabaab, like other terrorist groups, has expressed a desire to attack U.S. interests at home and abroad,” the official said. “That’s a serious concern, especially since they’ve shown the ability to attract some Americans to Somalia.”

Bruce Riedel, a former CIA analyst who was an adviser to President Obama on Afghanistan-Pakistan strategy, said the Somali refugee crisis both in Yemen and the United States creates a significant national security issue and an opportunity for the terrorist organization to find recruits at home and abroad.

“These attacks show for the first time that al Qaeda’s Somali affiliate can strike outside the horn of Africa,” said Riedel, who is a counter-terrorism analyst for the Brookings Institution, a nonprofit think tank in Washington, D.C. “Now we have to worry that they can activate supporters inside the American Somali community to strike here as well.”

The Examiner reported in May that al Qaeda was attracting recruits from among the approximately 700,000 Somali refugees who fled their war-torn nation to the impoverished East African nation of Yemen.

“Al Qaeda’s leadership in Yemen has very ambitious plans to develop cooperation [with] al Shabaab in Somalia,” Riedel said. The group looks to control shipping lanes in the Bab el-Mandeb strait that separates Asia from Africa and is the world’s energy choke point, Riedel said.

Al Shabaab spokesman Sheik Ali Mohamud Rage said Monday that Sunday’s bombs were “months in the making,” according to reports. The spokesman told reporters that the attacks were revenge for Uganda’s participation in a peacekeeping force supporting the Somali government.

The incidents underscored concern among intelligence and federal law enforcement officers about the group’s ability to recruit new members, specifically in the United States.

In 2008, more than 20 men in their late teens and early 20s traveled to Somalia after being recruited in the United States by members of the radical group.

The FBI opened an investigation after information revealed that the men — mostly from the Minneapolis-St. Paul area — joined the terrorist group. Some of the young men became suicide bombers for the organization, and the FBI continues to solicit the help of the Somali community to track other missing men.

In April, The Examiner published details of a law enforcement report that 23 Somalis who entered Mexico illegally earlier this year were released there in late January before receiving a full security screening.

It was later discovered that one of the Somalis, Mohamed Osman Noor, 35, was believed to be a member of al Shabaab. Intelligence obtained by U.S. and Mexican authorities suggested he and four others were planning to enter the United States through the Laredo border in Texas.

Michael Braun, former administrator and chief of operations at the U.S. Drug Enforcement Administration, said “many global security experts have failed to comprehend the speed at which terrorist groups like al Shabaab are evolving, both organizationally and operationally.”

The Horn of Africa — and especially Somalia — has become a terrorist haven where many young men share both the Muslim religion and an anti-U.S. perspective with al Qaeda.

Terrorist organizations such as al Shabaab and others in the region “are all heavily involved in the global drug trade and are now occupying the same ungoverned space in Africa,” Braun said.

“We had better wake up and understand that these groups are coming together in permissive environments like Africa, sharing lessons learned, establishing rock-solid relationships and growing a nefarious, global capacity,” Braun said.