Ten people were wounded, one critically, in clashes between Yemeni security forces and southern separatists in Aden on Saturday, medical sources said, days after six were shot dead during protests.
The separatists want political autonomy or a new state in south Yemen. It is one of three insurgencies in the strategically vital Arabian Peninsula state where Washington fears political chaos is giving al Qaeda space to operate.
North and south Yemen were unified in 1990 after the Communist-led southern government collapsed. Northern forces won a brief civil war four years later after the south tried to secede from the union.
The secessionist movement gained strength during mass, nationwide street protests against former president Ali Abdullah Saleh in 2011, which forced the veteran strongman from office a year ago.
On Thursday, security forces shot at dozens of secessionists in Aden as they staged a rally against Saleh's successor, President Abd-Rabbu Mansour Hadi, a northerner. There were also armed clashes in another southern town, al-Dalea.
Medical sources and witnesses said at least six people had been killed during the two clashes.
Southern Yemenis complain of discrimination by the government in the north. The impoverished state also faces a rebellion by the Shi'ite Muslim Houthi movement in the north and an insurgency in some southern areas by Islamist militants allied to al Qaeda.
Tackling lawlessness in the country, which lies near oil shipment routes and flanks the world's top oil exporter, Saudi Arabia, is seen as important by Western and Gulf countries.