A prominent international rights group says Yemen's Houthi rebels had stored explosives in a warehouse in a residential area in the capital that caught fire last month, killing at least 15 children and wounding more than 100 people.

The New York-based Human Rights Watch and an independent Yemeni rights organization released a joint statement on Thursday urging the Houthis to "stop storing large concentrations of volatile materials in densely populated areas."

In Yemen's civil war, the Iran-backed Houthis have been fighting a Saudi-led military coalition backing Yemeni President Abed Rabbo Mansour Hadi's forces since March 2015.

The Houthis control the capital, Sanaa.

The statement said the initial cause of the fire remains unknown. However, it cited media reports saying Saudi-led forces had launched an airstrike in this area that day.