"The island of Gran Canaria, where over 20,000 hectares of pineland has burnt down, is seeing the worst situation, and 13,000 hectares of forests have been destroyed on Tenerife," the source said.
However, the spokesman said the fires were raging in inland areas of the islands, while coastal regions where numerous hotels and popular beaches are located were under no threat.
The official said strong winds and scorching temperatures of up to 45 degrees Centigrade (113 degrees Fahrenheit) were helping to spread the blaze, with firefighters unable to use heavy machinery in mountainous districts.
He said five water carrying helicopters and a hydro plane were currently involved in the firefighting operation over Tenerife, and more aircraft were expected to arrive soon.
However, a resident of the village of Aldea de San Nicolas on Gran Canaria complained about "a lack of firefighting equipment" in a telephone conversation with RIA Novosti.
Spanish Environment Minister Cristina Narbona arrived in the fire-hit region earlier in the day to coordinate firefighting efforts, while local authorities have already pledged up to 300,000 euros in compensation to the affected households.