Authorities and militants take Nairobi battle to Twitter

Al-Shabab say this picture shows two of their fighters in the Westgate complex

While international attention has been drawn to the dramatic stand-off at the Westgate shopping complex in the Kenyan capital Nairobi, both Kenyan authorities and al-Shabab militants have been trying to broadcast their messages about the attack on social media.

Even before the Westgate shoot-out, al-Shabab had been trying to use English-language Twitter accounts to broadcast its message to the wider world. However, accounts thought to be used by the group had already been shut down by Twitter twice in the past nine months.

Each time, however, the account has re-appeared under a slightly different name.

During the attack on Westgate, an al-Shabab linked account began putting out messages saying the attack was in retaliation for Kenyan forces' "crimes" in Somalia and referring to "fighting the Kenyan kuffar [infidels] inside their own turf".

That account in turn was suspended and others have appeared over the course of the siege, all of them using similar language, causing confusion over which one, if any, was genuine.

Gloating

On Tuesday yet another account was created, and an al-Shabab spokesman confirmed to the BBC that it was their account. As of Tuesday afternoon, it was still active.

Like the previous accounts, it has also taken to gloating over the attack and urging Kenyans to put pressure on their government to withdraw forces from Somalia.

One message reads: "You could have avoided all this and lived your lives with relative safety. Remove your forces from our country and peace will come #Westgate."

The battle for the narrative over the attack has been fought in parallel with the stand-off

The account also tweeted a photo originally posted by another, mainly Arabic-language, account affiliated to al-Shabab claiming to show two of the attackers inside the shopping complex.

This feed has managed to stay on Twitter since being set up on 1 May. It has also been giving updates during the current crisis, some of them in English.

Clearly aware of how the crisis is being covered in the international media, it refers to rumours that Samantha Lewthwaite, the British widow of one of the bombers that carried out the 7/7 attack in London in 2005, is involved in the Westgate attack, even using the "white widow" nickname given to her in the press.

Confusion

Kenyan security officials have also been tweeting prolifically throughout the crisis, with police providing many announcements in the form of tweets.

The inspector general of Kenya's national police service, David Kimaiyo, announced after the crisis began on Saturday that the area was surrounded by police and appealed for the public and media organisations to stay away from the scene.

He has been giving a regular stream of updates ever since, as has the account for the Kenyan police.

However, verifiable facts about the situation inside the mall have at times been difficult to come by, with an apparent lack of co-ordination in the messages being given by different branches of government.

For example, on Monday the Kenyan Foreign Minister Amina Mohamed said in a US television interview that "two or three" Americans and one British woman were among the attackers.

On the same evening her cabinet colleague Joseph Ole Lenku sent a tweet stating: "All terrorists are male".

Also on Monday evening several official accounts began to suggest the crisis was drawing to a close. "We're in control of #Westgate", read one message from the interior ministry, while other accounts linked to Kenyan security forces retweeted congratulatory messages about the operation.

Kenyans have been lining up to donate blood for the victims of the attack

However, it soon became clear that the operation was in fact continuing and that not all of the attackers had been apprehended.

But arguably the most important use of social media by the authorities is to rally Kenyans behind the security forces as they respond to the attack using the hashtags #WeAreOne and #WithOneAccord, a reference to the Kenyan national anthem.

The prevailing mood among Kenyans on Twitter appears to be one of support for the operation against the militants and a feeling of solidarity in a time of crisis.

Kenyans are among the most active users of Twitter in Africa and have also been using social media in order to come together and organise initiatives to help the victims of the attack.

Many shared information about where to give blood - blogger Robert Alai shared a picture of children on roller-skates holding placards urging Kenyans to donate blood.

Others shared stories of Kenyans bringing food to journalists covering the siege and the security forces posted near the centre.