Yemeni loyalist forces fought street battles with guards from a powerful tribal federation whose leader has sided with protesters demanding an end to President Ali Abdullah Saleh's rule, witnesses said on Tuesday. At least four gunmen were killed in the clashes, which dimmed prospects for a political solution to a transition of power tussle following a nearly four-month-old revolt inspired by protests that swept aside the leaders of Egypt and Tunisia. "The clashes were violent. The sound of machinegun and mortar fire could be heard everywhere. I saw smoke rising from the entrance of the interior ministry," one witness told Reuters. The shooting, in the sandbagged streets surrounding a fortified mansion belonging to the wealthy and politically powerful al-Ahmar clan, pitted loyalist forces against guards of Sadiq al-Ahmar, head of the Hashed tribal federation from which Saleh also hails. Four tribal guards were killed, and six other people were wounded, an opposition leader said. Fighting in the same area of the capital on Monday killed seven people, among them a bystander, a police officer and five tribal gunmen.