DUBAI (Reuters) - The United States said it launched its first attack on Islamic State’s deadly Yemen branch on Monday with a series of nighttime airstrikes that residents said targeted two villages and killed several people.

Unmanned U.S. drones launched around 12 missiles at militant positions in Yakla and al-Abl in southern al-Bayda province, according to local people living nearby, who declined to be named due to safety concerns.

They said the number of casualties caused by the attack was not immediately clear because locals were too afraid to approach the site as U.S. aircraft hovered over the area for hours.

The Pentagon said in a statement that U.S. forces had killed dozens of Islamic State members in a strike on two camps where fighters trained in using machine guns and grenade launchers.

Residents disputed that account, saying the fighters targeted actually hailed from a powerful al Qaeda affiliate who deployed in the area to fight Iran-aligned Houthi militiamen as part of Yemen’s civil war, which began in 2015.

The complex conflict pits a kaleidoscope of tribes, military units and political factions against each other in chaotic rivalries that have allowed hardline Sunni Muslim militant groups like al Qaeda and Islamic State to thrive.

The United States provides arms and logistical support to a Saudi-led military coalition that has launched almost daily air strikes against the Houthis to try to restore Yemen’s internationally recognized government.

Al Qaeda in Yemen, one of the fiercest branches of the global network, has plotted to down U.S. airliners and claimed responsibility for the 2015 attacks on the office of Charlie Hebdo magazine in Paris.

It has been targeted by U.S. air strikes for a decade.

Islamic State, which only launched its first bombing in Yemen as it careered toward civil war in March 2015, has claimed responsibility for a series of spectacular attacks on military and civilian targets which have killed hundreds of people. (reut.rs/2ghdNRx)

Yakla, one of the sites targeted in the strike, was the site of a U.S. raid in January targeting suspected al Qaeda militants which local medics said killed 30 people including 10 women and children, and also left a Navy SEAL dead.