HODEIDAH, Yemen (Reuters) - An air strike by the Saudi-led coalition fighting in Yemen killed 12 civilians on Monday in the coastal city of Hodeidah, medics and a witness said, and the Houthi rebels later targeted Saudi Arabia’s southern border area with a missile.

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Medics and a civilian who saw the wreckage said the air strike had destroyed a house in the al-Hali district, where displaced civilians from other provinces were settled.

The 12 victims were all from the same family including seven children, they said.

A spokesman for the Saudi-led coalition said: “We take this report very seriously and it will be fully investigated as all reports of this nature are - using an internationally approved, independent process. Whilst this is ongoing, it would be inappropriate to comment further.”

Hodeidah is home to the impoverished country’s biggest port from where most of the humanitarian aid reaches millions of civilians on the brink of famine. The operation of the port, controlled by the Iran-aligned Houthis, was not affected by the air strike.

Saudi Arabia and the United Arab Emirates intervened in a civil war in Yemen in 2015 against the Houthis to restore the internationally recognized government of President Abd-Rabbu Mansour Hadi.

The alliance, which includes other Sunni Muslim states, has conducted thousands of air strikes targeting Houthi fighters and has often hit civilian areas, although it denies ever doing so intentionally.

The war has killed more than 10,000 people, displaced more than 2 million and driven the country - already the poorest on the Arabian Peninsula - to the verge of famine.

The Houthis, in turn, have launched rockets into Saudi territory with mixed results.

On Monday, a missile targeted the border area of Dhahran al-Janub. The coalition said it fell 1.75 km inside Yemen, but the Houthi-run Saba news agency said it hit a Saudi military base causing unspecified casualties. Reuters was unable to independently verify those claims.

Last week the Houthis launched a flurry of missiles which Saudi Arabia said it had intercepted over Riyadh. Debris from the missiles fell on a home, killing one person.

Rights watchdog Human Rights Watch on Monday said the Houthi attack had violated the laws of war by indiscriminately targeting populated areas.

“The Houthis should immediately stop their indiscriminate missile attacks on populated areas of Saudi Arabia,” said HRW’s Middle East director Sarah Leah Whitson.

“But just as unlawful coalition air strikes don’t justify the Houthis’ indiscriminate attacks, the Saudis can’t use Houthi rockets to justify impeding life-saving goods for Yemen’s civilian population.”

When the Houthis fired missiles at Riyadh last November, the coalition responded by shutting Yemen’s airports and ports. The United Nations said that blockade raised the danger of mass starvation, and it was partially lifted.