AL MUKALLA, Yemen — The heat was stifling, the power out. So the transients, mostly women and children displaced from nearby towns, ventured outside their temporary housing on Monday for some air, witnesses said. Then the Saudi warplanes struck.

In what medics and residents in Yemen’s western port city of Al Hudaydah described as an instant midmorning slaughter in a residential housing area, the warplanes fired missiles at the civilians, cutting them to pieces as they sought relief from the 92-degree temperature. At least 14 were killed and nine wounded.

The Saudi authorities, who contended that the targets had been military, said they were looking into the circumstances behind the airstrike in Al Hudaydah, the only Yemeni port that remains under the control of Yemen’s Houthi rebels after more than three years of war.

But the airstrike was a reminder of the lethal hazards facing unarmed Yemenis from the firepower wielded by the Saudi-led coalition, despite its repeated pledges to spare civilians in its campaign to crush the Houthi-led insurgency.