Firefights between police and southern separatists in Yemen on Friday killed five and wounded 23, as protesters nationwide denounced a plan granting the president immunity from prosecution, medics and police said.
"Three protesters were killed and 18 others were wounded," a medical official in the main southern port of Aden said of the southern separatists.
"Two policemen were killed and five others were wounded," said another medic from a government hospital in the city.
The official named one of the dead as Major Walid Saleh Ali, whom police had earlier said was among two policemen wounded.
Witnesses said police used tear gas and live rounds against thousands of demonstrators in Aden's Khor Maksar district.
The protesters were calling for secession and to reject a Gulf-brokered plan that grants President Ali Abdullah Saleh immunity from prosecution when he steps down.
Gunmen among the protesters returned fire, the same sources said.
Witnesses said protesters were still battling the police later on Friday for control of Al-Arud Square where the gathering took place.
Police said they intervened because of the "sensitivity of the location."
The square is close to consulates, UN offices and security headquarters.
"We allowed them to gather at the beginning but later they began to spread so we had to intervene," a police official told AFP.
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The Southern Movement protesters called for separation, marking the anniversary of clashes on January 13, 1986 between factions of the Yemeni Socialist Party that ruled south Yemen, an independent state at the time.
"The Southern Movement is boycotting the upcoming presidential elections across all southern provinces," read their banners. "The Gulf Initiative does not concern us."
Based on the Gulf plan, Saleh will remain honorary president until February 21 when Vice President Abdrabuh Mansur Hadi will officially replace him.
"The southerners affirm that they reject the elections and the Gulf initiative and hold on to their demand for the secession of the south," said Khaled Awadh, a Southern Movement activist and one of the organisers.
Meanwhile, tens of thousands of people protested in Sanaa and 17 other provinces calling for Yemeni unity and rejecting the Saleh immunity deal.
"No north. No south. Our unity is in the hearts," their banners read. "The Yemenis have decided, they must be freed."
In addition to southern calls for separation, Shiites and Sunni extremists have clashed in the north, while youths in the capital's Change Square have fought over the Gulf deal signed by the parliamentary opposition.
A security official said 20 gunmen were killed on Thursday in clashes between Zaidi Shiite rebels and Sunni Salafist gunmen in north Yemen.
Protesters, whose ranks have seen hundreds of deaths in the crackdown by Saleh's forces on their movement since last January, want those accused of killing demonstrators to face justice.
"No immunity, no guarantee to Saleh and his aides," they chanted.
The immunity law was drafted on Sunday by the transitional government that was formed after Saleh signed the Gulf plan. Parliament has yet to convene to ratify the law.