* Tribal sources say drone attacked three cars
* Suspected militants killed deputy governor this week (Adds witness)
By Mohamed Ghobari
SANAA, April 19 (Reuters) - An air strike killed 13 suspected al Qaeda militants in the central Yemeni province of al-Bayda on Saturday, security and tribal sources said.
"An air strike targeted cars that suspected al Qaeda militants were in and killed 13 of them in the Sawma'a area of al-Bayda," a security source told Reuters.
The tribal sources said a drone had been circling al-Bayda for days and on Saturday struck two cars the suspected militants were in. Three civilians who happened to be in a nearby car were also killed, they said.
Yemen has been fighting Al Qaeda in the Arabian Peninsula (AQAP) - regarded by Washington as one of the most lethal wings of the group - but AQAP still manages to carry out significant attacks against security forces in the poor Arab country.
Stability in Yemen is a top priority because of the country's location next to oil exporting giant Saudi Arabia. Riyadh also watches AQAP with concern since the branch was founded by citizens of both countries and has sworn to bring down its ruling al-Saud family.
Nasser Salem, a witness who arrived at the scene after the strike, said: "We found a completely burnt car and body parts strewn around and we started picking them up," he told Reuters.
The United States has stepped up drone strikes as part of a campaign against AQAP, which is based in Yemen.
Yemen is among a handful of countries where the United States acknowledges using drones, although it does not comment on the practice.
Earlier this week, suspected al Qaeda militants shot dead the deputy governor of al-Bayda as he was leaving his home, according to a security official.
Al-Bayda has seen serious security incidents in the past. In December, 15 people on their way to a wedding were killed by an air strike after their party was apparently mistaken for an al Qaeda convoy, according to security officials.
The Yemeni government said in a statement at the time that senior al Qaeda militants were targeted in the air strike. It did not say who carried out the attack.
AQAP's leader recently appeared in a video addressing a large gathering of fighters somewhere in Yemen and vowed to attack the United States. (Writing by Yara Bayoumy; Editing by Tom Heneghan)