Gunmen attacked a police headquarters in the southern Yemeni port city of Aden on Saturday, killing 10 security men, and a police official said the attackers freed several detainees.

Yemen is struggling to curb a growing separatist movement in the south and cement a ceasefire with Shi'ite rebels in the north. It is under international pressure to quell domestic conflicts to focus on an al Qaeda presence in the country.

The gunmen entered the building and freed an unspecified number of people held at the intelligence police headquarters before leaving, a police official told Reuters in Sanaa.

'There were 17 casualties among security forces, 10 killed and seven wounded,' the local police official said.

There was a heavy exchange of gunfire for more than an hour with the gunmen, who wore military uniforms, and smoke rose from the area, which also houses the state television building in the southern port city, residents told Reuters.   

The police official said the attack caused a fire at the building, which was being brought under control.   

Yemen leapt to the forefront of Western security concerns after the regional Al Qaeda wing claimed responsibility for a failed attempt to bomb a US-bound airliner in December.   

Al Qaeda's Yemen branch threatened on Friday to respond to a government crackdown against it in eastern Yemen, calling on local tribesmen to take up arms against the government.   

A military operation of shelling and gunfights, launched in the eastern province of Maarib last week, sought to catch suspected Al Qaeda gunmen believed to be behind the ambush of a Yemeni military convoy that left a commander and a soldier dead.-Reuters