At least four people were killed and dozens of others wounded Sunday in the Yemeni capital Sanaa in clashes between security forces and supporters of the Shi\'ite Houthi group. An interior ministry official told Xinhua that clashes erupted after protests of supporters of the Houthi group turned into violence against the guards of the National Security Bureau (NSB). \"They were demanding the release of their colleagues whom they claimed were arrested by the NSB during 2011 unrest,\" the official told Xinhua by phone on condition of anonymity. Several soldiers were injured during the clashes. However, the security forces managed to disperse the protesters from NSB headquarters in central Sanaa, he said without elaborating further. Meanwhile, Houthi spokesman Ali al-Bukhaity said four members of the group were killed and more than 20 others injured by bullets of the NSB\'s guards. He said in a statement obtained by Xinhua that Houthi supporters demanded the release of their colleagues while they were approaching the building of the NSB. He added that dozens of Houthi supporters were arrested by the NSB during the uprising against former president Ali Abdullah Saleh in 2011. Saleh resigned in February 2012 after a year of mass protests that left more than 2,000 people killed and hundreds of others arrested. Saleh\'s then deputy Abd-Rabbu Mansour Hadi was elected as new president for a two-year interim period, in line with a power transfer deal brokered by the Gulf Cooperation Council and backed by the United Nations. Witnesses said security reinforcement was seen in the area around the intelligence building following the clashes. The clashes broke out one day after Hadi announced the second round of the country\'s national reconciliation dialogue, in which Houthi group and other Yemeni political forces joined in. The dialogue, which is part of a UN-backed power transfer deal, was launched in March 18, aiming to draft a new constitution and prepare for holding the presidential election by the end of Hadi\'s two-year transitional period in February 2014.