Israel is signaling a wider campaign against Houthi militants in Yemen, a mountainous and impoverished country more than 1,000 miles from Israeli territory.

Israeli forces unleashed a series of strikes on the Yemeni capital, Sanaa, and the western city of Hodeidah on Thursday, killing at least six people and injuring dozens more, the Iran-backed Houthis said in a statement where it vowed to retaliate.