The U.N. humanitarian coordinator in Yemen has decried the killing of 13 civilians, including seven children, in a large explosion over the weekend in the rebel-held capital, Sanaa.

Lise Grande described the killings in a statement Monday as "terrible, senseless deaths and injuries and we offer our deep condolences to the families of the victims."

The cause of Sunday's blast at a warehouse remains unclear, which Yemeni officials say injured over 100 people and damaged nearby schools.

The Houthi rebels, who gained control of the capital in 2014, said the Saudi-led coalition had targeted the warehouse with an airstrike. The coalition denied carrying out any strikes in the area.

Yemen's internationally-recognized government said the rebels had stored weapons at the warehouse.