(The Telegraph) — A statement from Ansar al-Sharia, a Yemeni group affiliated with Al-Qaeda in the Arabian Peninsula (AQAP), claimed responsibility for the attack, which happened during a rehearsal for a National Unity Day parade scheduled for Tuesday.
It said it was a response to the security forces' "crimes" – an apparent reference to the all-out assault conducted by government troops in recent days to check al-Qaeda's advances in a vicious civil war in the south of the country.
There had been rumours for some days that an attack was imminent. One analyst, who asked to remain anonymous, told The Daily Telegraph several days ago that an incident in Sana'a, which has up to now been spared the worst of the violence, was "inevitable".
"The government is attacking a hornets' nest – eventually, one of the hornets will retaliate and sting," he said.
The soldiers were lined up for the parade rehearsal in Sabaeen Square in the centre of the city, near the presidential palace, yesterday morning when one of their number triggered an explosive device.
Some of those at the scene said he was a member of the Central Security Force, a paramilitary group whose chief of staff is Yahya Saleh, nephew of the former president, Ali Abdullah Saleh, who stepped down earlier this year in the face of Arab Spring protests.
However, military uniforms are easily available in the city and it is possible he was an infiltrator.
Witnesses said the explosion left clothes, blood and body parts strewn across the parade ground, which also serves as one of the capitals major road arteries. Several severed heads lolled in the dust.
"There are no words to describe this," said Ahmed, a military cadet, looking at the blood-strewn aftermath of the explosion. "Those behind this are not even human."
The bombing appeared to be a failed assassination attempt against Maj Gen Mohammed Nasser Ahmed, the minister of defence, who arrived at the heavily secured city square to greet the assembled troops just minutes before the blast.
By Monday evening, the official death toll was put at 96, with up to 300 injured.
Until now, Sana'a has been relatively calm, if tense, since the end of the fierce factional fighting of much of the past year which eventually led to the end of Mr Saleh's 33-year rule.
But while his internationally-backed retirement in favour of his deputy, Abdo Rabbu Mansour Hadi, ostensibly solved the country's political crisis, Monday's attack underlined the fragility of the capital's shattered peace.
In response, Mr Hadi sacked two generals loyal to Mr Saleh, including another of his nephews, Ammar, who was director of national security.
The attack comes amid a renewed government offensive against Ansar al-Sharia, a militant group that took advantage of Yemen's growing power vacuum to seize control of swathes of territory in the country's southern Abyan province.
It is being heavily supported by intelligence and air support from the United States, which sees Yemen as a new front line in the war against al-Qaeda. Several failed terrorist attacks on its territory, including those of the so-called "underpants bombers", originated with AQAP.
In 2010, the British ambassador and deputy ambassador also both survived terrorist attacks in Sana'a.
Abdulghani al-Iryani, a Yemeni political analyst, said: "Rather than being a show of strength, today's senseless attack is a sign that al-Qaeda and Ansar al-Sharia, if they are indeed responsible, are increasingly feeling as if they are in a weak position."