A car bomb has exploded in the car park of Madrid's Barajas Airport, injuring at least four people.
The government says Eta has ended the ceasefire
Two police officers who were examining the vehicle parked close to terminal four were among those injured.
The government said Basque separatist group Eta had carried out the attack - ending a ceasefire declared in March.
The Eta ceasefire came after four decades of violence aimed at creating an independent Basque state in the north of the country.
Saturday's blast sent a plume of dark smoke high into the skies.
Flights in and out of terminal four have been halted, and there is chaos at the other three terminals, officials say.