The Basque separatist group ETA claimed responsibility for a car bombing Saturday that left one person missing and several others slightly injured in a parking lot at Madrid's international airport, Spain's interior minister said.

Alfredo Perez Rubalcaba told reporters the blast ends a nine-month ceasefire the group had declared after four decades of violence aimed at creating an independent Basque state in the north of Spain.

The explosion followed warning calls from the Basque separatist group ETA.
(Daniel Ochoa de Olza/Associated Press)

"I want to firmly condemn this attack," he said, adding that Prime Minister Jose Luis Rodriguez Zapatero would have more to say to the country later in the day.

A Spanish Interior Ministry official earlier said two calls had been received by police, the first a warning, the second specifying the type of vehicle and claiming it was the work of ETA.

Twenty-six people were hurt, most of them with damage to their ears from the shockwave, officials said.

Police cordoned off the parking lot and began looking for suspect vehicles. Two officers involved in the search were among the injured, according to state radio.

The blast at Barajas Airport halted air traffic to the facility's newest terminal on one of the year's busiest travel days. The blast shattered windows, damaged several floors of the multi-storey carpark and sent smoke into the terminal building, forcing an evacuation.

Hundreds of passengers gathered outside on the airport tarmac. Flights returned to normal by early afternoon and were not affected at the other three terminals.