Play was halted at the Madrid Open tennis tournament, while the Spanish capital's metro system ground to a stop.

The countries have a combined population of over 50 million people. It was not immediately clear how many people are affected.

A massive power outage appears to be affecting large portions of Spain and Portugal Monday. Red Electrica, the operator of Spain's power grid, said early Monday morning it had begun its plan to restore electricity and that the cause of the outage was being analyzed.