Mogadishu, Somalia - Kenyan security forces continued to battle their way through an upscale Nairobi mall on Tuesday that al-Shabab gunmen seized four days ago.
Officials say at least 62 people have been killed in the attack on the Westgate shopping centre, and more than 170 wounded. The figures are expected to rise once the siege finally ends and the mall is secured.
The mall attack is the most significant strike in Kenya since al-Qaeda bombed the US Embassy in Nairobi in 1998, killing more than 200 people. Somalia-based al-Shabab - established in 2006 after Ethiopian troops invaded that country - has claimed responsibility for the brazen assault.
The Islamist group has lost ground in recent years to Somali government soldiers and African Union peacekeepers. Linked to al-Qaeda, al-Shabab enforces a strict interpretation of Sharia, or Islamic law, in all areas under its control.
Attacks by the group within Kenya’s borders were unheard of before October 2011, when Kenyan troops established their presence in Somalia.
|Alleged members of al-Shabab are blindfolded by soldiers [AP]
Of the five countries contributing troops to the African Union Mission in Somalia (AMISOM) - Burundi, Djibouti, Kenya, Sierra Leone and Uganda - al-Shabab’s animosity appears directed most towards neighbouring Kenya.
"Al-Shabab have lost more territory to Kenyan troops than to any other AMISOM troops-contributing country," said Abdullahi Boru, a Nairobi-based Horn of Africa security analyst.
After months of indirectly arming and training local militias inside Somalia to fight the Islamist group, Kenya decided to send its troops into Somalia on October 2011.
What followed for al-Shabab was the continuous loss of much of its prized territory. Until then, the group had controlled most towns along the Kenya-Somalia border.
"Kenya is our historic enemy. Kenya is the enemy of the Somali people and Somalia," Sheikh Abulaziz Abu Muscab, spokesman for al-Shabab's military operations wing, told Al Jazeera.
Some of the areas al-Shabab lost during the Kenyan campaign were lucrative farming and fishing regions. With the loss of such territory came a strain on the group’s finances.
Response to Kismayu’s loss?
Last September, after a year of fighting al-Shabab in Somalia, Kenyan forces succeeded in pushing the group out of the key port city of Kismayu.
Before they were driven out, al-Shabab had controlled Somalia's third-biggest city for more than four years. It was the group's main base of operations and its loss was a big hit.
"Al-Shabab has lost Kismayu port, which was their lifeline. They are in survival mode," said Hussein Arab Isse, Somalia’s former deputy prime minister and defence minister.
"Shopping malls are easy targets and Westgate is the biggest mall in Kenya. It is possible they targeted the mall as a response to the loss of Kismayu," he added.
They [Kenya] bombed our civilians in refugee camps. They bombed innocent Somalis in Gedo. Ask them why they continue killing our people first.
Even before they went into Somalia, Kenya openly backed militia leader Sheikh Ahmed Madobe in his bid to oust al-Shabab from the Jubba region of Somalia.
Madobe was a senior al-Shabab figure before he fell out with the group and took up arms against his former brothers-in-arms.
Once al-Shabab was vanquished, the Kenya government backed Madobe as its chosen leader for the taken over areas. It wasn’t an easy pill to swallow for the Islamist fighters, seeing their former ally rewarded for turning his back on them.
"Worst possible choice of leader. Backing Ahmed Madobe only gave al-Shabab more reasons to fight the Kenyans," said Boru.
Kenya is also the only country in AMISOM - a combined force of more than 17,000 soldiers - to have deployed its air force and navy against the Islamist militia, a move al-Shabab says resulted in civilian deaths.
"They bombed our civilians in refugee camps. They bombed innocent Somalis in Gedo. Ask them why they continue killing our people first," said Abu Muscab, when Al Jazeera asked about the civilian carnage in the Westgate mall attack.
Bringing the fight to Kenya
In 2011, after suffering a spate of kidnappings of foreigners on Kenyan soil, Kenya's then-internal security minister George Saitoti accused the Islamist group of being behind the abductions.
In 2012, Aboud Rogo, a Muslim cleric and a vocal supporter of the Islamist group, was killed in Mombasa in a drive-by shooting. Rogo was on a UN and US sanctions list for allegedly recruiting fighters and obtaining funds for al-Shabab.
Nine months later, another cleric Ahmed Khalid - a close friend of Rogo and a staunch supporter of al-Shabab - was killed in a police shootout, according to Kenyan authorities.
"It is widely thought they were killed for their support for al-Shabab. Many people think those killings were extrajudicial killings," said the security analyst Boru.
After the killings, al-Shabab’s stance against Kenya became even more hardline.
|An al-Shabab fighter at a rally near Mogadishu [AP]
"We don’t believe Kenya is a good neighbour. We don’t trust them. They are the enemy," said the spokesman Abu Muscab.
Kenyan President Uhuru Kenyatta - whose nephew was killed in the mall attack - has said his government will not be dissuaded by the assault.
"I want to be very clear and categorical: We shall not relent on the war on terror. We will continue that fight," Kenyatta said.
Al-Shabab, meanwhile, has called on Kenya to withdraw its troops from Somalia, or face more attacks on Kenyan soil.
Hussein, who was Somalia’s defence minister at the height of al-Shabab’s rule in south and central Somalia, said he thinks a resolution will not be achieved through military force alone.
"To find a solution to al-Shabab, there needs to a negotiation," Hussein said.
Achieving security in the Horn of Africa is also up to the Somali people themselves, he added.
"Somalis are the only ones who can find a solution to this problem, and it won’t be just from the military."
Follow Hazma Mohamed on Twitter: @Hamza_Africa