At least 37 people have died in fighting on Tuesday night as clashes intensified in the Yemeni capital Sanaa, doctors and officials said, according to BBC. Violence escalated after a ceasefire broke down between security forces and fighters loyal to Sheikh Sadiq al-Ahmar, head of a tribal confederation. Analysts say the conflict threatens to drag Yemen into civil war. Yemen is facing increasing unrest in several areas after President Ali Abdullah Saleh refused to step down. Witnesses reported heavy fighting in the capital overnight as both sides blamed each other for breaking the ceasefire.