Militants attacked a Yemeni army base in the country's south, a local official said on Saturday, highlighting a security breakdown just weeks ahead of a presidential election aimed at ending a year of political upheaval.

One militant was killed in the attack on Friday night on the base on the outskirts of Lawdar in Abyan province, the official said. Explosions and heavy exchanges of gunfire were heard throughout the city, residents said.

Lawdar was the site of a US drone strike that killed at least 12 militants earlier this week amid a swell of violence in the south, where Islamist fighters suspected of links to al Qaeda have seized several towns.

Weakened by a year of protests against outgoing President Ali Abdullah Saleh, Yemen's government is facing challenges from al Qaeda-linked militants who have seized territory in the south and frequently attack state troops and offices.

The United States and Saudi Arabia fear al Qaeda's regional wing is strengthening its foothold there, near oil shipping routes through the Red Sea.

Separately but also in Abyan, gunmen opened fire on a group of tribesmen, killing one and wounding two. Some tribes have joined forces with the army to try to regain territory grabbed by militants.

Saleh's opponents accuse him of manipulating the threat of militancy to scare Washington and Riyadh into backing him as the only bulwark against an al Qaeda takeover in the impoverished state.

An election to choose Saleh's successor is scheduled to take place later this month. Both southern separatists and rebels in the north have said they will boycott the vote, and militants last week attacked an office of the electoral committee.-Reuters