Protesters from a religous insurgent group, the Houthis, build tents in Yemen's capital, Sanaa, on Sunday.<br/> <br />They want to cut off the road to the main airport and the interior ministry, as the army bombs their rebel positions in the north.<br/> <br />The demonstrations -- which have been going on for months -- quickly escalate into violence.<br/> <br />Houthi leader, Khaled al-Madani, says clashes will only strengthen their resolve.<br/> <br />(SOUNDBITE) (Arabic) HOUTHI LEADER, KHALED AL-MADANI, SAYING:<br/> <br />"Our reaction to the attack will be more escalation and more revolutionary activities to overthrow the government and achieve our goals".<br/> <br />Some fear for the stability of Yemen, which contains many of the same sectarian rifts that have set ablaze other Arab countries.<br/> <br />The Heaths -- which belong to a branch of Shi'ite Islam -- launched their uprising against Yemen's government in 2004.<br/> <br />The country is mostly Sunni.<br/> <br />Several bitter wars have been fought since.<br/> <br />The He
