Authorities have struggled to reduce armed attacks on the streets of Yemen Sanaa - Ali Rabea Yemeni President Abed Rabbo Mansour Hadi has vowed to crackdown on armed gangs operating in Yemen, after meeting the families of security personnel killed and wounded in clashes with gunmen in the western Yemen city of Hudaydah. Four armed men opened fire on the officers and soldiers of the central security on Wednesday, in an attack sources said was linked to the ownership of private land. Meanwhile, two security officials were wounded when gunmen, believed to be supporters of the Yemeni opposition group Southern Movement, attempted to storm the main security headquarters in the southwestern province of Dali. The Yemeni Interior Ministry issued a statement on its website in which it claimed that armed groups had thrown hand grenades and opened fire on Dali\'s central security management building with \"light and medium-sized weapons.\" The statement added that the ministry refused to respond to the attack, due to the risk of aggravating an already tense situation in the province. \"Two security men were wounded in the attack, and were transferred to the hospital. They are in good condition,\" the statement concluded. On the diplomatic front, several southern Yemeni leaders abroad held a meeting with the former Yemeni Vice-President Ali Salim al-Beidh in Beirut, to unify their positions on the transition process and the ongoing national dialogue in Sanaa. Meanwhile, two southern leaders from the League Party, Abdul Rahman al-Jafari and Mohsen bin Farid al-Awlaki, have urged the UN Special Envoy for Yemen, Jamal Benomar, to hold a meeting between southern opposition forces. The move came after Benomar identified the southern groups as a challenge to political transition in Yemen, during his address to the UN Security Council in a behind closed-doors session. Benomar described the opening of the National Dialogue Conference as a \"major milestone for Yemen’s political transition,\" before adding that \"serious challenges remain, including unrest in the south of the country , where a civil disobedience movement is now attracting large numbers to the streets.\" \"The calls for secession have grown. After nearly two decades of discrimination, repression, and un-addressed legitimate grievances, the people in the south are weary and sceptical of promises of reform. \"The Yemeni Government will need to undertake immediate confidence-building measures in the south to address the long-standing grievances of southerners over unlawful or illegitimate seizure of property and unjust dismissals from military and civil service,\" Benomar explained.