Nearly 100 people were killed and at least 200 injured when a suicide blast targeted a military parade rehearsal in Yemen's capital Sana'a on May 21.

The bomber, dressed in military uniform, detonated his explosives in the middle of soldiers rehearsing for a parade to mark the 22nd anniversary of the unification of North and South Yemen.

Al Qaeda (AQAP) have apparently claimed responsibility for the attack, in revenge for what it described as the US war against it in southern Yemen. However, many Yemenis have expressed their doubts.

The following video [ar] shows the immediate aftermath of the explosion on Sabaeen Street in Sana'a [WARNING: DISTRESSING IMAGES].

Journalist Tom Finn was at the scene:

@tomfinn2: In Sabaeen. Police everywhere, pieces of flesh scattered over the tarmac. Injured all in hospital. ‪#yemen‬

@tomfinn2: Ambulances still racing around Sana'a. Doctors say hospitals are overwhelmed. ‪#Yemen‬

Yemen Updates tweeted a very graphic photo of some of the soldiers killed in the suicide bombing, and Ibrahim Mothana tweeted a link to a graphic video.

Farea Al Muslimi, a student activist based in Beirut, commented:

@almuslimi: This is a terrifying day in ‪#Yemen‬ and at the same time golden chance for [President Abdou Rabbo Mansour] ‪#Hadi‬ to take urgent strong measures in restructuring the army.

President Hadi indeed issued a decree [ar] after the attack replacing top security officials, including a nephew of former president Ali Adullah Saleh.

Mai Saleh tweeted:

@A4Mai: Fadhel AlQawsi is appointed as the new commander of the Central Security forces by decree of President ‪#Hadi‬ ‪#Yemen

She added:

@A4Mai: So Ammar [Saleh's nephew] is out? Did we have to witness a disaster for these decrees to come? ‪#Yemen‬

The site of the suicide bomb attack in Sana'a, Yemen that claimed the lives of at least 96 soldiers. Photo by Luke Somers, copyright © Demotix (21/5/2012).

Although some news sources have stated that Al Qaeda has claimed responsibility for the attack, many are waiting to learn more.

Yemen scholar Gregory D. Johnsen commented:

@gregorydjohnsen: Less rumor mongering please about today's attack in ‪#Yemen‬. I promise it is ok to say: “I don't know”

And demanding more evidence, Mai Saleh tweeted:

@A4Mai: Would love to see that ‪#AQAP‬ statement in which it claimed responsibility for the attack ‪#Yemen‬

News of Yemen Revolution Facebook page posted that 12 hours prior to the explosion, a pro-Saleh page on FB predicted the explosion and provided a link, which was subsequently removed.

Mohammed wondered how the suicide bomber went unnoticed:

@Yemen4Change: ‪#Yemen‬ | the word is: the suicide bomber was wearing military clothes & a belt packed with explosives, NO ONE NOTICED? ‪#Sanaa

‬While Farea Al Muslimi asked:

@almuslimi: Why didn't ‪#Saudi‬ help by intelligence info about ‪#AQAP‬ as it did regarding the bombs being sent to ‪#US‬? ‪#Justwondering‬ ‪#YEMEN‬

Amid the many speculations and question marks, Yemen's Human Rights Minister Hooria Mashhour tweeted:

@Hooria_Mashhour: Transparent investigation should be done for all these mass crimes against humanity ‪#yemen‬

Ataf Alwazir, a prominent Yemeni activist and blogger, encouraged people to look deeper than the repetitive news circulating:

@WomanfromYemen: always keep an open mind & dont take everything as it is. Dont be a copy paste person. Question & analyze. Thats why we have a mind.

The day of the blast was certainly one of the saddest days Sana'a and Yemen have ever seen. The attack raises questions regarding the efficacy of the joint US-Yemeni counterterrorism strategy, and give credence to the argument that US drone strikes are counterproductive and simply fuel extremism.