Dozens of people are reported dead as renewed fighting between government forces and a powerful tribal group pushes Yemen closer to civil war.
The breakdown of a ceasefire saw fresh clashes in the capital Sanaa. Around 40 people were killed overnight say officials and medical sources.
Separately, there has been violence in Zinjibar, a town seized by Islamist militants according to loyalists of embattled President Ali Abdullah Saleh.
His troops have fired on protesters in Taiz. The chief UN human rights envoy is investigating reports that at least 50 people have been killed there since Sunday.
Saleh is under mounting pressure to sign a Gulf-led deal to end his three-decade rule and stem the spreading chaos.