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.

The fires in Spain this year have burned 158,000 hectares or 610 square miles, according to the European Union’s European Forest Fire Information System. That is an area roughly as big as metropolitan London.

Spain on Friday warned of "very high or extreme fire danger in most of the country," as firefighters there continue battling 14 blazes in temperatures up to 104 degrees Fahrenheit.