This is a few days old, but the WSWS article is a lot more enlightening than anything I've seen in the mainstream press:
...What is known is that a squad of men dressed in police uniforms entered the shrine in the early hours of the morning and overcame the mosque guards. At dawn, they detonated explosives that had been rigged in such a fashion as to collapse the entire building. The famous golden dome of the 1,000-year-old mosque—which was erected in 1905 and was one of the landmarks of modern Iraq—was reduced to rubble.
It was a particularly provocative act. Shiites regard Al-Askariya as one of the four holiest sites. Two ninth century Shiite saints are buried there. According to Shiite theology, it is where Mohammad al-Mahdi, the 12th and last imam, will return and restore justice after a time of great evil. The movement headed by cleric Moqtada al-Sadr, which has its base among Iraq’s urban poor, calls its militia the “Mahdi Army” after the saint and preaches that his return is imminent.
--snip
He wrote: “The Shia are crazy about this
. I am Sunni and I am frightened that if I do not go somewhere to be surrounded by those who can protect me then they make take out their anger on me. We were not alone on the roads. There were many cars with families in them. Then even more surprisingly there was the sight of the black-shirted followers of Moqtada al-Sadr with their Kalashnikovs at many of the street corners. There were police out as well but they are standing with them... I have seen such a thing before in Najaf but never in Baghdad. It frightened my wife. ‘There is the smell of civil war everywhere,’ she said to me.”
With violence spreading across the country, the government Prime Minister Ibrahim al-Jaafari—himself a Shiite fundamentalist—declared an unprecedented day and night curfew yesterday. The announcement will do little to reassure Sunni communities. Most of the Iraqi soldiers and police are Shiite. The British Times reported, for example, that Iraqi troops had “cheered and waved” as militiamen raked a Sunni mosque with bullets. American troops have taken up positions in major Sunni suburbs and at key religious sites in Baghdad, just days after most of the capital was ceremoniously “handed-over” to a predominantly Shiite division of the new Iraqi military.
http://www.wsws.org/articles/2006/feb2006/aska-f24.shtml