On Saturday 21 September 2013, unidentified gunmen attacked Westgate shopping mall, the most upscale mall in Nairobi, Kenya. The attack resulted in at least 67 deaths, and more than 175 people were reportedly wounded in the mass shooting.
The extremist Islamic group al-Shabaab claimed responsibility for the incident, which it characterised as retribution for the Kenyan military's deployment in the group's home country of Somalia. Many media outlets also suspected the insurgent group's involvement in the attack based on earlier reprisal warnings it had issued in the wake of Operation Linda Nchi from 2011 to 2012.
Kenyan authorities arrested dozens of people in the aftermath of the attack, but had not announced any suspects directly related to the siege. On 4 November 2013, a Kenyan court charged four Somali nationals with harbouring the gunmen in their homes, with each pleading not guilty.
On 20 September 2015, Foreign Policy magazine reported the Westgate attack on 21 September lasted several hours, with the last victim killed before special Kenyan security forces entered the mall, which was also corroborated by New York City Police Department, HBO, and United States Army. The mall was officially declared secured on 24 September.