Battle rages in Yemeni capital - Heavy fighting continues across Sanaa, with witnesses saying security forces have fired live bullets at protesters !

Yemeni forces loyal to entrenched ruler Ali Abdullah Saleh have faced off with tribal fighters in Yemen's capital in clashes that killed dozens as a US envoy flew around the region to try to stop a looming civil war.

Street fighting in Sanaa, which grew out of protests against Saleh's rule since January, has killed at least 135 people in the past 10 days, calling into question the future of an impoverished Arab state already near economic disaster.

Heavy fighting continued late into the night on Thursday, with witnesses saying security forces had fired live bullets at protesters in the capital - no injuries were reported.

State television showed live pictures of the Yemeni Airways building ablaze and blamed tribesmen for setting it on fire. It is reported that the fire had started after government troops targeted the nearby home of Sadiq al-Ahmar, a prominent tribal leader.