It has been a truly terrible day in Yemen, with more than 40 people reported dead as a result of attacks on demonstrators by the president's supporters in Sana'a. Although armed conflict is common in Yemen, there has been nothing like this in the capital for many years.

The Egyptian Chronicles blog has some photographs, but beware – they are very graphic.

The official news agency, meanwhile, in the old Soviet tradition, is reporting mass rallies around the country backing President Salih.

Possibly the regime was hoping that with eyes turned on Libya this would escape attention, but the US has condemned the violence in no uncertain terms. 

A statement from President Obama said:

"I strongly condemn the violence that has taken place in Yemen today and call on President Saleh to adhere to his public pledge to allow demonstrations to take place peacefully.

"Those responsible for today's violence must be held accountable.

"The United States stands for a set of universal rights, including the freedom of expression and assembly, as well as political change that meets the aspirations of the Yemeni people.

"It is more important than ever for all sides to participate in an open and transparent process that addresses the legitimate concerns of the Yemeni people."

The situation in Yemen is looking increasingly insoluble. The problem is not merely how to get rid of Salih but what will happen after he goes. The longer he clings on, the more difficult it will be to achieve a peaceful transition – and it may even be too late for that already.

Posted by Brian Whitaker, 18 March 2011. 

UPDATE, 19 March: Human Rights Watch has issued a statement about the killings, calling for an immediate suspension of military aid to Yemen.