Iraqi authorities say the bombers were two women, described as "mentally ill." They also say the bombs were remotely detonated. Here's how one eye witness described what happened: the woman came to this market at 10 in the morning and said she had some birds to sell. So bird vendors gathered around her. Then when more people gathered, the blast occurred. You can see the massacre, this is an unprecedented massacre. (Tell us what officials said about these women and why they think the women were coerced into carrying these bombs?) The officials were very clear that these were mentally ill women. The women were known to the populations around these markets and that's one of the reasons it's thought they were tricked in some way, the aim to get the women past security. It's not clear how the officials know this. They do not it was a bombing involved explosives wrapped to the body and they found the extremely cleanly severed heads which is an indication of that. (Well if indeed these women were unwilling or mentally ill, is this a sign that the tactics of the insurgents are changing?) The tactics of the insurgency have changed over the last five years. They've been able to adapt very quickly to each step that the US and Iraqi forces have taken. The US Ambassador says it's a sign they're under pressure. That might be fair enough. It's going to new and more barbaric means. The surge and political deals have put insurgents under siege. One official speculated that the drop off of the number of people being killed is directly related to the security measures. He said that the insurgents were finding themselves unable to place bombs in advance. That was why until today casualty figures were down. There is a feeling security has been stepped up. (It wasn't stepped up around these markets. Is that because they hadn't experienced violence lately?) I think that's fair to say. And it's one of those dreadful typical Iraqi ironies that this attack was the result of the success of the surge, that people felt they could go out again. (We know the Shia cleric Moqtada al Sadr, the truce and ceasefire called by him is about to expire. How concerning is that?) it's a matter of deep concern. They think Sadr's organization is fraying. One diplomat said this is a pivotal year for Iraq, both in terms of security and politics.