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What you need to know:

Saturday September 21, 2013 The siege begins
Sunday September 22, 2013 Shooting continues
Monday September 23, 2014 A loud explosion is heard
Tuesday September 24, 2013 Operation ends

Approximately 1230pm Saturday, September 21, 2013: Armed men stormed the Westgate Shopping Mall in Nairobi, killing at least three people and sparking a fierce gun battle.

The scene of crime where many were killed after gunmen stormed the Westgate Mall in Nairobi September 21, 2013.

At the time, the motive of the attack was not immediately clear. An hour into the attack, spokesman for the Kenya military Major E Chirchir posted on his official Twitter account:

This screen grab released on October 18, 2013 and taken from closed circuit television shows one of the gunmen during the attack at the Westgate Mall on September 21, 2013.

1230hours Terrorists fired shots at innocent bystanders.

This screen grab released on October 18, 2013 and taken from closed circuit television shows people crawling on the ground during the attack at the Westgate Mall on September 21, 2013.

Three hours later, AFP reporters at the scene said the surrounding area had been sealed off by police.

A police officer takes his position outside the Westgate Mall in Nairobi on September 21, 2013.

1300hours Kenya Red Cross secretary general Abbas Gullet and his team arrive at the scene.

Kenya Red Cross arrive at the Westgate Mall in Nairobi September 21, 2013.

1330hours All four terrorists join up at Nakumatt supermarket and shoot people found hiding at the store.

A screen grab released on October 5, 2013 and taken from closed circuit television shows the gunmen inside Nakumatt Supermarket at the Westgate Mall on September 21, 2013.

Mr Abdul Haji, a licensed gun holder, beckons to a child fleeing from danger at the Westgate shopping mall on September 21, 2013.

INFOGRAPHIC: Timeline of events during Westgate attack

1350hours Inspector General of Police David Kimaiyo arrives at the scene, says: "There's an incident at Westgate and we're urging the public to keep off the area."

Inspector General David Kimaiyo at the scene of crime where many were killed after gunmen stormed the Westgate Mall in Nairobi September 21, 2013.

One policeman ran to the rooftop only to discover participants of a kids cooking competition shot, injured and some dead. He ran back down to call for help.

A police officer at the Westgate Mall in Nairobi September 21, 2013.

The top floor where a kids cooking class was taking place at the Westgate Mall on September 21, 2013 in Nairobi.

An artist's impression of the late Ruhila Adatia Sood who was gunned down while attending a cooking competition at the Westgate Mall on September 21, 2013.

Kenya Red Cross at the Westgate Mall in Nairobi September 21, 2013.

1700hours Nation reporters at the scene have counted 26 bodies. Government appeals to Kenyans to donate blood. The Interior Ministry asks the public to leave the Westgate area for security reasons as the military joins the operation.

Kenya Defence Forces (KDF) arrive on September 22, 2013 at the Westgate mall in Nairobi. Every year in Kenya and across the world, children barely out of their teens are answering the call to die for what they are told is their religious duty.

An armoured personnel carrier at Westgate Mall in Nairobi September 21, 2013.

An image grab taken from AFP TV shows Kenyan troops taking position inside the Westgate Mall on September 21, 2013.

An image grab taken from AFP TV shows a Kenyan soldier inside the Westgate Mall on September 21, 2013.

Kenyan troops take position inside the Westgate Mall on September 21, 2013.

Ms Chepkorir, one of the survivors of the attack, hugs her husband after she was rescued on September 22, 2013.

1900hours CCTV shows all four terrorists in a storeroom at Nakumatt. They appear relaxed, took time to pray and tended to their colleague who was injured during the exchange of gunfire with police.

A screen grab released on October 18, 2013 and taken from closed circuit television shows the gunmen praying inside a room at the Westgate Mall on September 21, 2013.

Sunday, September 22, 2013: One of the three remaining terrorists tilted the CCTV camera so it could no longer cover the inside of the room. This was the last video footage of the terrorists. It is believed that they tried to escape using an unknown route. Journalists and volunteers kept vigil outside.

Kenyan journalists wearing bullet proof jackets and helmets film outside the Westgate mall on September 22, 2013.

At one point, loud explosions rented the air forcing volunteers, journalists and even police to run for cover.

Volunteers run for cover after hearing gunshots outside the Westgate shopping mall on September 23, 2013.

Volunteers and a policeman run for cover after hearing gunshots at Westgate shopping mall on September 23, 2013.

A grenade at the Westgate Mall in Nairobi September 21, 2013.

A Kenyan police officer guides volunteers as they run for cover after hearing gunshots at the Westgate shopping mall on September 23, 2013.

Monday, September 23, 2013: 0645hours A large explosion is heard inside the mall. A few hours later, four more large explosions are heard and smoke is seen rising up from the mall.

Smoke seen billowing above the Westgate mall on September 23, 2013. Photo/COURTESY

1900hours Kenyan officials say the smoke is from terrorists burning mattresses at Nakumatt. It later emerged that the Kenya Defence Forces decided to fire a high-explosive anti-tank rocket as part of their operation to neutralise the terrorists. The end result was the partial collapse of the rear rooftop parking lot and two floors with Nakumatt.