The toll climbed overnight as six of the critically wounded succumbed to their injuries, according to medics.

The slaughter in the capital Sanaa on Friday afternoon was the bloodiest day in weeks of unrest that has shaken the regime of President Ali Abdullah

Saleh, a key US ally in the war against Al-Qaeda militants on the Arabian Peninsula.

Witnesses said pro Saleh "thugs" rained bullets from rooftops around a square at Sanaa University, the centre of demonstrations seeking the end of Saleh's 32 year rule.