The attacks on a popular Nairobi mall that killed 68 people will attract more youth to al-Shabaab, the terrorist group claiming responsibility, says a University of Calgary terrorism expert.

The group, which seeks to establish an Islamic state in Somalia, focuses on recruiting youth as militant fighters —​ shabaab means youth in Arabic. Al-Shabaab has been facing increasing pressure from Kenyan forces in recent years but the Nairobi attack could serve to show potential recruits the group is still in the game.

"If you are a young, impoverished, radicalized Somali man — almost always a young man — you will say, 'These guys are still in business, al-Shabaab is not defeated by the Kenyan authorities, I want to join them because they're winners," said Barry Cooper, a security analyst with the University of Calgary.

Over the last several years, there have been reports of young, Somali-Canadian men joining al-Shabaab. 

In 2009, one federal Canadian official estimated as many as 30 Somali-Canadian youths may have been recruited by the group, and the U.S.'s Federal Bureau of Investigations and Britain's MI5 say similar numbers have left both the U.S. and the United Kingdom. 

Al-Shabaab has been heavily targeted by Kenyan military forces since 2011, when the military crossed the border into southern Somalia to pursue militants.

The move followed several high-profile kidnappings of foreign aid workers and saw Kenyan troops coordinating their efforts with Somali government soldiers to try and prevent al-Shabaab from operating in the region.

"This was not an attack on the government of Kenya. It had two purposes — one was revenge for what the Kenyan military had done in southern Somalia. They've been there since 2011 and they've weakened al-Shabaab in the area, and that's important," says Cooper.

"The other purpose is what the 19th-century terrorists called propaganda by deed. It was a way of showing their supporters, the radical Islamist supporters ... that they are still in business."

Attacks demonstrate al-Shabaab's 'professionalism'

While Cooper says the attack probably won't be treated the way 9/11 was in North America, it will still serve to give the group more credibility, both as a viable option for supporters and as a legitimate threat by Kenyans and others in the region.

"They're clearly capable of carrying out a fairly sophisticated attack, on what is admittedly a fairly soft target, but they put this together with a certain amount of professionalism," he says.

Part of the allure for youths joining militant groups like al-Shabaab is the sense that they are taking control or becoming empowered, said Ray Boisvert, former assistant director of the Canadian spy agency, CSIS, told CBC News in April. 

"It's about vulnerable youth, falling prey to a nasty subset of religious ideology driven through al-Qaeda narrative, being driven by a sense of adventure, a sense of purpose, a sense of meaning in their life," Boisvert said at the time.

Since entering Somalia, Kenyan and African Union troops have taken control of the capital, Mogadishu, and almost completely forced out al-Shabaab.

The city had previously been a centre of operations for the group since the 2009 Battle of Mogadishu, when al-Shabaab militants captured the capital. 

"Simply the attraction of acting, for a lot of these people, is extremely important," said Cooper. "It's a lot better than just being on the receiving end of an African military force."