The Somalia-based militant group al-Shabaab has claimed responsibility in the wake of the attack on an upscale Nairobi mall that left more than 60 people dead, including 2 Canadians, and 175 others injured.

Experts say that the al Qaeda-linked group targeted the Westgate Mall in Nairobi in part to exact revenge for Kenya's military involvement in neighbouring Somalia. Kenyan troops were deployed to Somalia in October 2011, where they joined African Union forces in a bid to push al-Shabab out of the nation's capital, Mogadishu.

An estimated 4,000 Kenyan troops remain in the country, fighting militants in the war-torn south.

But who just is al-Shabaab?

Al-Shabab -- whose name in Arabic means 'The Youth' – traces its roots to the military wing of the now defunct Somali Council of Islamic Courts. Al-Shabaab rose to prominence in 2006, after fighting Ethiopian troops that were backing the Somali government during a two-week battle.

Ahmed Abdi Godane is the leader of the group, though he is rarely seen in public. His predecessor, Moalim Aden Hashi Ayro, was killed in a U.S. air raid in 2008. Although it is difficult to estimate the total number of al-Shabaab members, most reports suggest fewer than 9,000 people including several hundred foreign fighters recruited outside Somalia.

“Al-Shabaab is primarily a domestic insurgency and 90 per cent or more of its members are only interested in overthrowing a Western-backed government and installing the Sharia law in Somalia,” says Bronwyn Bruton, the deputy director of Washington D.C.-based Africa Center.

For the most part, the group carries out its activities inside Somalia, where it has staged deadly suicide attacks in Mogadishu and Kismayo.

According to reports, al-Shabaab controls many rural areas and imposes its own strict form of Sharia law, including stoning to death women accused of adultery and amputating limbs of accused thieves.

Bruton said a splinter faction of the group made up of foreign radicals have been operating in Somalia since 2007.

“(They) are global jihadist and who are probably responsible for this strike in Nairobi,” she said.

The group formally pledged its loyalty to al Qaeda in February 2012.

Kamran Bokhari, vice-president of Middle Eastern and South Asian affairs at Stratfor Global Intelligence, says al-Shabab should be considered the al Qaeda of Africa. Its agenda, he says, is to attack non-Muslims and create a Muslim dominated world.

Although the combination of recent military losses coupled with infighting have left al-Shabaab weak, he says the latest attack in Kenya may be a demonstration of the group's might as it tries to re-establish legitimacy.

"They choose the target because it would make a big splash on media. I mean, a mall in Kenya frequented by Westerners and tourists including diplomats … this was something that was planned to make that splash and get that attention," Bokhari told CTV’s Canada AM on Monday.

Bokhari added that suicide bomber attacks on 'soft targets' such as hotels and malls should be seen as the new face of war.

"This is the future of warfare for at least some time to come," he said.

Christian Leuprecht, political science professor at Queen's University, suggested there was another strategic reason for the attack against the upscale Westgate Mall: it is Israeli-owned. Witnesses inside the mall Saturday suggested that the gunmen were targeting non-Muslims.

"A target was chosen in mind with also sending a message more broadly with regards to people that al-Shabaab in particular dislikes. And that is, of course, Israel and anything that is associated with Jewish culture," he told CTV News Channel.

According to Leuprecht, terrorism involving al-Shabaab in Kenya is not entirely new. The group targeted an Israeli jet in the country in 2002, as well as an Israeli-owned hotel in Mombasa, in addition to a number of smaller attacks in Nairobi.

Leuprecht said that al-Shabaab has lucrative economic stakes in the region that fund their activities. According to a United Nations report, al-Shabaab's income in 2011 was estimated between $70 million and $100 million.

In Canada, Leuprecht says that al-Shabaab activities mainly involve recruitment.

Leuprecht also said the recent attack is important because it clearly shows the group has little care for human life.

Al-Shabab took to Twitter to claim responsibility for the Westgate Mall attack late Saturday. “The attack at #WestgateMall is just a very tiny fraction of what Muslims in Somalia experience at the hands of Kenyan invaders."

Al-Shabaab is one of the more tech-savvy al Qaeda-linked militant groups. In the past, Twitter has shut down the group’s existing accounts, only to have new ones pop up in their place within days.

Al Shabaab has also long been vocal against any involvement, including from the African Union, inside Somalia.

"For long we have waged war against the Kenyans in our land, now it's time to shift the battleground and take the war to their land," al-Shabaab's Twitter account read.

"There will be no negotiations whatsoever," said another tweet.