SANAA: A Houthi official on Monday warned the US it would receive a "painful response" if it entered the war in Yemen, where Saudi Arabia has reportedly requested Washington's help in dealing with the group as it weathers repeated attacks.

Yemen's civil war – in which a Saudi-led military coalition supports the government against the Iran-backed Houthis – reignited in July, months into the wider regional conflict that has roiled energy markets and plunged the Middle East into risis.

The Houthis quickly began targeting Saudi oil facilities, tankers and transport hubs, including a string of lethal strikes on Riyadh's airport, rocking the world's top oil exporter.

Blasts resounded over the capital again on Monday night, with the Saudi coalition saying it had intercepted a Houthi missile and the group saying it had again targeted the airport.