SANAA : Fierce clashes broke out Saturday between pro-government tribesmen and Shiite Huthi rebels near the Yemeni capital, as the president vowed that authorities will not tolerate any violence.The Huthis - also known as Ansarullah - have advanced from their northern mountain strongholds towards the capital in a suspected attempt to expand their sphere of influence as Yemen is reorganised into six regions.Fighters from the two sides clashed, using machine guns and medium weapons, in the villages of Darwan, Bani Maymun, Al-Jaef and Al-Maamar, in the northern town of Hamdan, around 10 kilometres (six miles) from Sanaa International Airport, tribal and army sources said. Further north in Amran province, tribal and military sources said ‘fierce clashes’ pitting troops against Huthi militants raged late on Friday.The sources spoke of ‘dozens’ of casualties but AFP could not immediately verify the toll. Meanwhile, in a speech marking the start of Ramadan, the Muslim holy Muslim month of fasting, President Abdrabuh Mansur Hadi denounced the violence. ‘We will not allow any acts of violence here and there by any party trying to undermine security,’ Hadi said in a statement carried by state news agency Saba.‘All parties must comply with agreements reached to resolve latest tensions and fighting in Amran, Hamdan, Arhab, and Bani Matar’ in the north, he said. Huthis have been battling the central government for years from their Saada heartland, complaining of marginalisation under former president Ali Abdullah Saleh, who stepped down in 2012 after a year-long uprising.Clashes erupted anew earlier this month in the north, ending an 11-day truce agreed after mediation backed by United Nations envoy Jamal Benomar. The rebels say a federalisation plan agreed in February after national talks as part of a political transition would divide Yemen into rich and poor regions. They seized areas of Amran province in fighting with tribes in February that killed more than 150 people.In addition to the Shiite rebellion, a southern separatist movement and an Al-Qaeda insurgency, Yemen is also facing water, food, and fuel shortages. On June 11, thousands protested in the streets of Sanaa against the shortages as gunmen sabotaged power lines that left the country without electricity for days. The protests prompted Hadi to replace five ministers as authorities shut down a newspaper and television channel owned by Saleh, accused by his critics of impeding the country’s political transition.Electricity gradually returned to the country’s provinces but fuel shortages continued with long queues outside gas stations amid a total lack of diesel fuel, according to residents. Referring in his speech to the June 11 protests, Hadi said ‘we are still facing plots and significant attempts to impede’ the political transition in Yemen. He said Sanaa was on that specific day ‘deliberately emptied of oil derivatives as dozens of trucks carrying these derivatives from the provinces of Hodeidah and Marib were besieged days earlier.’Hadi however did not give further details or blame any parties for the incident. But days later Yemeni troops surrounded a mosque controlled by former president Saleh and Hadi removed heavy artillery from hills surrounding Sanaa over fears his predecessor, to whom some elements remain loyal, is plotting a coup. Saleh ruled Yemen for 33 years before being forced out in February 2012 and replaced by his long-time deputy Hadi under a UN- and Gulf-sponsored deal.