Anti-government protesters carry the body of a protester during a mass funeral in Sanaa, Wednesday (Reuters)
Battles erupted on Thursday between rival tribesmen in Sanaa's northern Al-Hasaba district, witnesses said, as fighting spread across neighbourhoods in the restive capital.
Gunmen of powerful dissident tribal chief Sheikh Sadiq al-Ahmar traded mortar rounds, machinegun fire and rocket propelled grenades with followers of Saghir bin Aziz, a tribesman loyal to President Ali Abdullah Saleh, the witnesses said.
Bin Aziz, who belongs to Yemen's most influential tribe Bakil, is also a Republican Guard officer and an MP.
Men loyal to Hemyar al-Ahmar, Sheikh Sadiq's brother who is also the deputy parliament speaker, joined the battles that soon gained momentum in the neighbourhood.
Sheikh Sadiq, one of the 10 sons of Sheikh Abdullah al-Ahmar, who was head of Yemen's parliament and Saleh's main ally until his death in 2007, is a key player in Yemeni politics.
He succeeded his father as head of the Hashid tribe and in March announced his support for protesters calling for the ouster of President Saleh, who has been in power for 33 years in deeply tribal Yemen.
Although the Bakil tribal confederation is larger in numbers than the Hashid, the latter is seen as the most powerful as it plays a stronger political role, observers say.