Somali militant group al-Shabaab has claimed responsibility for the deadly attack on a Nairobi shopping centre that left scores dead and others injured. Formed less than a decade ago, yet responsible for a string of attacks, the group has engendered a culture of fear through pockets of eastern Africa.
Though operating under the name Harakat al-Shabaab al-Mujahideen, the Islamist group is often referred to simply as al-Shabaab - meaning "the youth". Al-Shabaab was formed in 2006, emanating from the Islamic Courts Union that ran the Somali capital, Mogadishu, for six months before being driven from power.
Since then, the group has been said to engage in guerrilla warfare tactics against the Somali government and Ethiopian troops stationed in the country. It soon formally aligned itself with al Qaida, attracting hundreds of foreign fighters, including Britons.
Al-Shabaab has claimed responsibility for several deadly suicide bombings, including one in February 2009, which killed 11 Burundian soldiers on an African Union peacekeeping mission. The group carried out its first major international attack in July 2010 when it bombed the Ugandan capital, Kampala, killing at least 74 people.
A dominant force despite its size, al-Shabaab was dealt a blow in February 2012 after troops from the African Union force in the country (Amisom) succeeded in driving the Islamist group from Mogadishu. Hopes for an end to their reign of terror were further bolstered by reports that the al-Shabaab stronghold of Baidoa in the south west of the country had fallen to troops from neighbouring Ethiopia and Somali government forces.
Despite this, the group still exercises significant control over vast swathes of the south towards its border with Kenya.