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.

The latest round of strikes occurred as the United States and its ally Israel struggle to halt a campaign of regional assaults by Yemen’s Houthi militants.

The head of the World Health Organization (WHO) and other UN staff were at Yemen's international airport in Sanaa on Thursday during Israeli air strikes which are reported to have killed at least six people. WHO Director General Tedros Adhanom Ghebreyesus said they were about to board a plane when the attacks began.