PARIS, Oct 16 — Yemen’s Iran-backed Houthis have built up a missile and drone arsenal capable of launching varied and sustained strikes, as Saudi Arabia and the Yemeni government it backs are finding out.

Since early September, the Houthis have struck key oil infrastructure and airports across Saudi Arabia, notably Riyadh’s airport, which has been targeted 20 times.

They have also unsuccessfully targeted the cities of Medina and Mecca.

The trigger for their return to hostilities, after a four-year truce, was a Saudi bombardment of the airport in Sanaa, Yemen’s capital, in July to prevent a Houthi delegation from landing there.