Protests and gunbattles involving opponents of Yemeni President Ali Abdullah Saleh have left at least 12 people dead in Sana'a.

Activists and witnesses say at least eight of Saturday's deaths occurred when security forces opened fire on demonstrators who had gathered to rally against President Saleh. Witnesses say four others were killed elsewhere in the capital as security forces battled supporters of opposition tribal leaders and dissenting soldiers.

President Saleh has been facing increased calls for his resignation. He is also being pressured by Yemen's opposition and some world powers to sign a Gulf Cooperation Council initiative that calls for him to hand over power to a deputy.

The anti-government unrest has come at a time when the embattled leader is also dealing with militant-related unrest in some regions of Yemen.

Yemeni officials and tribal leaders say nine al-Qaida militants were killed on Friday in suspected U.S. airstrikes in the country's south.

They say the militants killed include a son of U.S.-born cleric Anwar al-Awlaki. The cleric, who had ties to al-Qaida's Yemen branch , was killed last month in a U.S. drone strike. Yemeni officials say the strikes also killed Ibrahim al-Bana, the media chief for the militant group's Yemen branch.

Hours after the airstrikes, suspected militants blew up a gas pipeline in what may have been a retaliatory act. Officials say operations were halted at a gas supply terminal as a result.