VILLANUEVA DE LA SIERRA, Spain, Aug 15 (Reuters) - Spain battled 14 major fires driven by high winds and aggravated by heat on Friday as authorities warned of "unfavourable conditions" to tackle flames that have already killed seven people and burned an area the size of London.

Spain was fighting 14 major fires, according to Virginia Barcones, general director of emergency services. Temperatures were expected to climb over the weekend.

Firefighters and military units are struggling to contain wildfires in northwest and western Spain as a prolonged heatwave intensifies the crisis.