Yemeni officials say police fired on demonstrators demanding the release of prisoners in the country's separatist south, killing three people.
Nine others were injured in the separate demonstrations on Saturday and Sunday.
Police officials say they were demanding the release of people arrested since violent demonstrations began on May 21 by southerners calling for power-sharing. Yemen's southerners, who complain of discrimination and government neglect, have expanded their demands to include independence.
North and south Yemen united in 1990, and rebels launched a failed bid for independence in 1994.
The police officials spoke on condition of anonymity because they were not authorised to speak to journalists.