Yemeni police on Wednesday opened fire at protesters in the southern city of Aden killing two civilians and wounding another two, on a "day of rage" called by separatists, medics said.
Police fired bullets and tear gas to disperse hundreds of Southern Movement supporters, witnesses said. Medics at a city hospital initially said a civilian was killed and three were wounded, but one of whom later died of his injuries.
The separatist Southern Movement called for southerners to mark a "day of rage" in tightly-patrolled Aden on the 16th anniversary of the port city being overrun by northern forces after a brief civil war.
The group also called on supporters to attend the funeral of an Aden resident, Ahmed Mohammed Darwish, who died last Friday in prison in the capital of former South Yemen.
Demonstrators were marching from a tent where the victim's family was receiving condolences to a state hospital to recover Darwish's corpse when the clashes erupted with police, witnesses said.
The crowds, estimated to number 300, were carrying portraits of Darwish and chanting "revolution, revolution south."
"The security forces detained six of the protesters after opening fire on us and dispersing our demonstration," a source from the Southern Movement told AFP.
Darwish died one day after he was detained along with dozens of others following a suspected Al-Qaeda attack on the city's intelligence headquarters on June 19.
Eleven people including seven military personnel were killed in the attack, officials said.
On Wednesday, armoured vehicles were deployed amid tight security measures in Aden, as the army sealed off the Khor Maksar district where the demonstration was held.
Yemen's interior ministry had urged "security services in several southern and eastern provinces to prevent outlaw elements from targeting security and stability through ... illegal demonstrations."
The Southern Movement is a coalition of groups with a range of demands from economic and social improvements to full independence for the regions of former South Yemen.
The impoverished country's south was independent from 1967 until 1990 when it united with the north. The south seceded in 1994, sparking a short-lived conflict that ended when the south was overrun by northern troops.