A series of intense Israeli airstrikes shook Yemen’s rebel-held capital and a port city early Thursday and killed at least nine people, officials said, shortly after a Houthi missile targeted central Israel.

Thursday’s strikes risk further escalating conflict with the Iranian-backed Houthis, whose attacks on the Red Sea corridor have drastically impacted global shipping. The rebels have so far avoided the same level of intense military strikes that have targeted Palestinian militant group Hamas and Lebanon’s Hezbollah, fellow members of Tehran’s self-described “Axis of Resistance”.