BARCELONA, JUNE 19 -- A car bomb killed 15 shoppers in a crowded Barcelona supermarket today and injured more than 30 in one of Spain's worst guerrilla attacks, police said.

Eight men, five women and two children died when the bomb exploded in the supermarket's underground garage.

In Barcelona's hospitals, doctors said they were unable to identify many of the victims because they were so badly mutilated.

Barcelona's Civil Gov. Ferran Cardenal told a news conference the bomb was placed in a Ford Escort which had been stolen in the Basque city of San Sebastian.

The blast came shortly after a caller claiming to speak on behalf of ETA (Basque Homeland and Liberty) telephoned a warning to the Catalan newspaper Avui that a bomb had been placed in the store.

The Basque organization, fighting for an independent Basque state, has set off several car bombs over the past few months in Madrid and Barcelona, host city for the 1992 Olympics.

{United Press International reported that an employe at the store said it had received a bomb threat two hours before the explosion, but that its managers had decided not to evacuate the building because it was not the first time a bomb threat had been received.}

The scene of the explosion was the Hipercor supermarket, owned by the Spanish department store chain El Corte Ingles. The store is in a working class neighborhood of Barcelona which, with a population of about 1.8 million, is Spain's second largest city.

The blast caused panic among shoppers. Witnesses said they saw one woman running out of the supermarket with her hair in flames.

Authorities called on doctors to report to hospitals and asked motorists to stay home to avoid slowing down ambulances.

The attack was the worst since a bomb attributed to a Middle East group killed 18 persons two years ago in a restaurant frequented by U.S. servicemen near the Torrejon air base outside Madrid.

If the responsibility is confirmed, today's blast will be ETA's worst attack on record. ETA killed 12 paramilitary Civil Guardsmen in Madrid a year ago.

Last week ETA blew up pipelines near Spain's biggest oil refinery, in Tarragona, south of here, setting off a huge blaze and causing damage estimated at $16 million.

Today's blast came shortly after Interior Minister Jose Barrionuevo told a news conference in Madrid that an ETA commando unit was at large in Barcelona.