A widespread and unexplained power outage knocked out electricity in most of Spain and Portugal on Monday, shutting off traffic lights and causing chaos at airports, train stations and on the roads.

Some 96 departing flights from Portuguese airports have been grounded so far, while 45 have been called off from Spain.

Several airports, including Madrid airport, which is Spain's busiest, had no electricity, El Mundo reported. Major cities including Barcelona, Seville and Valencia were without power. Parts of France were also affected by power loss.