52 protesters were killed on Friday in Sanaa (Yemen), as government security gunmen shot protesters at a rally calling for the resignation of President Ali Abdullah Saleh.
The escalation of state violence has led to several ministeral resignations in protest, including the Yemen ambassador to the United Nations. Yemen's most powerful tribal confederation (which includes Saleh's own tribe) has also called for him to step down.
Yemen in state of emergency after protest massacre, Reuters, 19 Mar 2011.
Yemen's UN envoy resigns over killings, Al Jazeera, 20 Mar 2011.