Yemeni security forces opened fire on protesters in the southern city of Taiz calling for President Ali Abdullah Saleh to resign, as fighting continued in the capital Sana'a on Thursday.
Dozens of people have been killed in Taiz this week, as security forces repeatedly used violence to disperse protesters gathered in al-Hurreya square, DPA reported.
In Sana'a, at least 15 people were killed in overnight fighting between security forces and tribesmen loyal to Sheikh Sadeq al-Ahmar.
Tribesmen from various parts of the country have been trying to enter the capital to join al-Ahmar's supporters in the fighting, resulting in clashes with security forces on the outskirts of the city.
Violence erupted in Sana'a last month after Saleh refused - for the third time - to sign a Gulf-brokered power transfer deal.
Sheikh al-Ahmar is the head of the Hashid tribe, to which Saleh belongs, and supports the widespread protests calling for the president to resign after 32 years in power.
Al-Ahmar's supporters claim the violence was triggered when security forces loyal to Saleh tried to storm Al-Ahmar's house.
As violence drags on and the death toll rises, neither Saleh nor the opposition parties show any signs of approaching dialogue.
Yemen has been in crisis for months, as nationwide protests demanding Saleh's resignation are met with brutal government crackdowns and efforts at political mediation have repeatedly failed.