Sanaa’s international airport was closed and flights were diverted to Aden in the south as heavy clashes erupted between tribesmen and Republican Guards in the capital Wednesday. Tribal sources said tribesmen belonging to Arhab, the tribe of preacher Abdul Majid Al-Zindani were engaged in running battles with the guards. The United States has categorized Al-Zindani as a \"terrorism financier\" and has put sanctions on him. Elsewhere, security forces and opposition tribesmen loyal to Sadeq Al-Ahmer clashed for the third straight day. Witnesses said dozens of armed tribesmen were killed Wednesday in gunbattles with the well-trained Republican Guard regiments in the Al-Hasbah neighborhood, near the house of Al-Ahmer. The witnesses could not give an exact figure for the fatalities. On Wednesday, Al-Ahmer\'s men occupied the ministries of trade and tourism and the building of the state-run news agency, Saba. Several tribal chiefs came under fire while trying to arrange a truce between the forces of Al-Ahmer and the government. The Republican Guards sealed the capital in an apparent attempt to prevent armed tribesmen from the neighboring provinces from entering the city. President Ali Abdullah Saleh was defiant in the face of international appeals for him to step down. He said he would neither offer any more concessions nor receive any orders from anyone \"We will confront any person who tries to cause chaos with all possible means at our disposal,\" Saleh told a group of foreign journalists in the capital. He said Washington has recently reduced its economic support for his country and now backs those who oppose him. \"Our relationships with the Americans were good in fighting terrorism but the Americans became less enthusiastic after chaos swept Tunisia and Egypt.\" On Wednesday, US President Barack Obama repeated his call for Saleh to quit. \"We call upon President Saleh to move immediately on his commitment to transfer power,\" Obama said at a joint press conference with British Prime Minister David Cameron in London. From Arab News