The Yemeni army has driven fighters associated with al-Qaeda from the key southern city of Zinjibar, a hard-fought objective that they had contested for a year.

Fighters calling themselves Ansar al-Sharia, or Supporters of Islamic Law, had occupied parts of Abyan province as well as Zinjibar, its capital, since the spring of 2011. The fighters, who are thought to be tied to al-Qaeda's branch in Yemen, declared the area an Islamic emirate.

But on Tuesday, the government pushed the fighters out of both Zinjibar and Jaar, a nearby town, during a fight that inflicted casualties on both sides.

Five soldiers were wounded after hitting landmines in Zinjibar, a military official told the AFP news agency.

The state-run SABA news agency said troops swept into Jaar early on Tuesday, sparking fierce clashes and forcing fighters to flee towards another Qaeda stronghold, the southern coastal town of Shaqra.

The fighters had controlled Jaar, like Zinjibar, for more than a year.

Clashes in the town between the two sides had left 28 dead, two of them soldiers, military and local officials said on Monday. The fighters had occupied an army-owned munitions factory in the town.

Locals said they saw vehicles carrying armed men, weapons and furniture heading east towards Shaqra. Fighting there over the past day has left eight fighters dead, a military official said.

The fighters distributed pamphlets in the town apologising to residents for dragging Jaar into a conflict with the army and for the damage caused by the fighting, according to locals.

Yemeni forces launched an all-out offensive on May 12 aimed at reclaiming towns and cities lost to Ansar al-Sharia.

The group took control of large swaths of southern Yemen during last year's turmoil linked to the uprising against then-president Ali Abdullah Saleh.

Since the offensive began, 485 people have been killed, according to an AFP tally combined from different sources. This includes 368 al-Qaeda fighters, 72 soldiers, 26 local armed men and 19 civilians.