Yemeni President Abdullah Ali Saleh thumbed his nose at the United Nations Security Council on Monday and refused to step down.

The 15-member Security Council on Friday unanimously called for Saleh to implement a transfer of power agreement brokered by the six-member Gulf Cooperation Council (GCC) immediately.

The agreement, which Saleh has backed out of several times before, calls for him to step down within 30 days. Saleh, however, has proven nonplussed by the world body or its demands and kept up the crackdown that began even before he returned from Saudi Arabia weeks ago.

Before Saleh's return from the kingdom, where he was recovering after a June assassination attempt, it was believed Saleh could be induced not to return. But Saleh has proven a crafty and determined political survivor who has shown no intention of ending his 33-year reign.

Clashes in the capital of Sanaa between government troops and armed followers of tribal leader Sadeq Al Ahmar broke out in the capital, hours after the UN Security Council called for Saleh's self-ouster on Friday.

AFP reported at least 10 people were killed in clashes Saturday. Witnesses said deafening explosions rocked the Al Hasba district, where the houses of Al Ahmar and his brother are located. On Sunday, at least 13 were killed as clashes continued unabated. At least two were teenage boys killed when a grenade was thrown into a market stall.

Also on Sunday, fierce clashes erupted between Saleh loyalists troops and soldiers loyal to dissident General Ali Mohsen Al Ahmar in the "Change Square" area of the capital, where thousands of protesters have encamped to demand Saleh's departure. Neither side would comment on their causalities.

Sadeq Al Ahmar, who heads the most powerful tribe in Yemen, Hashed, was formerly a close ally of Saleh. Sadeq and Ali Mohsen switched sides and joined with student-led protesters in publicly demanding Saleh go.

Clashes between these powerful factions have left hundreds of Yemenis dead and threatened to drag the impoverished country into full-blown civil war.

Saleh and those who would see him depart shared one point of commonality in that neither side was moved by the United Nations resolution.

"We were not waiting for any UN resolution. The resolution sided with the interests of the members of the council, not with the aspirations of the Yemeni people," Waled Al Amrai, an anti-regime activist, told Reuters.

Saleh did not respect the resolution and his forces immediately [after the resolution] fired on the people," Al Amrai added. "We see this as the UN granting Saleh 30 days to crush the revolution militarily."