(Recasts adding casualty details)
ADEN, Oct 16 (Reuters) - One al Qaeda militant and three tribesmen allied to the army were killed in an attack on a military checkpoint in southern Yemen, tribal sources said on Tuesday.
Yemen's wealthier Gulf neighbours and the United States are concerned that al Qaeda and other Islamist militants operating in Yemen could pose a threat to neighbouring top oil producer Saudi Arabia and to nearby shipping lanes.
On Tuesday, a vehicle carrying armed al Qaeda militants attacked an army checkpoint in the southern province of Abyan, touching off a firefight, the sources said. Another vehicle then approached the checkpoint and exploded in an apparent suicide bombing, killing its driver and the three tribesmen.
An initial account by tribal sources had said two al Qaeda militants and two tribesmen had been killed in the exchange of fire but tribal sources later said the four deaths had happened during the suicide attack.
The Yemen-based al Qaeda in the Arabian Peninsula and other militant groups strengthened their grip on parts of the country during an uprising that ousted veteran President Ali Abdullah Saleh in February.
Washington, wary of the growing power of al Qaeda, has stepped up drone strikes on suspected militant positions, with the backing of Saleh's successor, President Abd-Rabbu Mansour Hadi. (Reporting By Mohammed Mukhashaf; Writing by Maha El Dahan; Editing by Michael Roddy and Janet Lawrence)