Police believe a woman's attempt to kill a spider may have been behind an explosion at a home in Sydney's north.

Emergency services were called to a house in Kirribilli after an explosion blew out the bathroom and kitchen windows just after 1:00pm (AEDT) today.

A 66-year-old woman told police she was trying to kill a spider when she sprayed insecticide under her washing machine.

Fire investigators believe the spray triggered the explosion.