Airstrikes and artillery fire rocked the Yemeni city of Aden overnight as combatants battled for control of the main airport in fighting residents said was the worst in over a month of war.

Iran-allied Houthi rebels and local militiamen traded tank and mortar salvos in the Khor Maksar district near the airport from Wednesday evening into Thursday and warplanes from a Saudi-led coalition of Arab states bombed Houthi positions.

On the frontier with Saudi Arabia, a shell fired from Yemen killed a patrolling Saudi border guard on Thursday morning, the kingdom's Interior Ministry said, bringing the number of Saudi casualties in the campaign to 11.