Yemen's embattled president has vowed he will not step down or allow his impoverished nation to become a "failed state" even as urban combat between government troops and armed tribesmen engulfed parts of the capital.
Both sides raised the spectre of civil war as the three-day death toll rose to at least 63. The latest violence comes just days after a failed Arab mediation effort to end the three-month uprising and ease Ali Abdullah Saleh from power.
Mr Saleh's statement - read by spokesman Ahmed al-Soufi in a meeting with tribal allies - ruled out a voluntary departure and attacked US-backed efforts to negotiate his exit after 32 years of authoritarian rule.
"I will not leave power and I will not leave Yemen," the statement said. "I don't take orders from outside."
Mr Saleh also threatened that his ousting could turn Yemen into a haven for al Qaida - directly touching on US fears that chaos in Yemen could open room for more terrorist footholds. The Yemeni branch of al Qaida is linked to the attempted Christmas Day 2009 bombing of an airline over Detroit and explosives found in parcels intercepted last year in Dubai and Britain.
"Yemen will not be a failed state. It will not turn to al Qaida refuge," the statement said. Mr Saleh also said he would work to prevent the recent violence from "dragging the country into a civil war".
US President Barack Obama has called on Mr Saleh to transfer power, a change from an administration that once considered the Yemeni ruler a necessary ally against terrorism.
UN Secretary-General Ban Ki-moon called for an immediate end to the fighting, expressing concern that clashes "might further destabilise the situation", UN spokesman Martin Nesirky said at UN headquarters in New York.
The clashes broke out on Monday after Mr Saleh's troops tried to storm the compound of Sheik Sadeq al-Ahmar, the head of Yemen's largest tribe, the Hashid. Hundreds of tribal fighters rushed to the capital's northern Hassaba neighbourhood, where clashes erupted with government forces.
Government troops shelled the neighbourhood around Mr al-Ahmar's house while gunmen in civilian clothes exchanged gunfire and rocket-propelled grenades with tribal fighters.