Al-Shabaab militants have remained a thorn in the flesh despite concerted efforts by the international community to completely degrade them.

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In recent weeks, the group has launched deadly operations across East Africa, killing dozens of people in the process.

For instance, the group killed at least 11 police officers in Kenya in December alone. They are suspected to have also been behind Saturday's deadly attack in Mogadishu where close to 90 people died.

Even though the UN banned charcoal trade that had been their source of income, the group has managed to launch sophisticated attacks.

To finance itself, New York Times reports, the militants have set up an extensive racketeering system that levies fees on sales of agricultural produce in southern and central Somalia — areas that are the stronghold of the group. They also tax imports into the Mogadishu port, according to the United Nations.

The group’s growing assertiveness was in evidence when it declared war last year on pro-Islamic State groups in Somalia in a fight over territory.

“Al Shabab is still strong and stable,” said Stig Jarle Hansen, the author of “Horn, Sahel and Rift: Fault-lines of the African Jihad.”

With heavy finances from the mafia-style taxation, the group has managed to run active recruitment and execution of the attacks.

A fortnight ago, the group abducted four construction workers in Wajir before taking off with two businessmen in Garissa last week.