Yemen’s Houthi armed group has shot down seven US Reaper drones worth more than $200m in recent weeks, marking the most significant material loss yet in Washington’s campaign against the fighters.

Three of the drones were lost in the past week alone, suggesting an improvement in the Houthis’ ability to strike high-altitude US aircraft.

The drones – each costing about $30m – were conducting surveillance or attack missions when they crashed into water or land.