MADRID, Spain (AP) _ Tens of thousands of Spaniards marched through downtown Madrid on Tuesday to shout their frustration over Basque separatist bombings and shootings blamed for 19 killings this year.

Many of the estimated 250,000 marchers demanded stiff punishment for the Basque separatist group ETA, which was blamed for a car bombing in Madrid on Monday that killed a Supreme Court judge, his driver and bodyguard, and injured 35 others.

``Life in prison,'' they chanted. Others called for an immediate crackdown to stop the violence.

``The government has to make penalties harsher,'' said Sonia Rull, a 33-year-old secretary. ``Everything can't remain the same after 800 deaths.''

ETA has claimed some 800 killings in its 32-year war for independence in the Basque region that straddles the border between Spain and France.

Earlier Tuesday, Prime Minister Jose Maria Aznar and other Spanish leaders joined mourning relatives of two of the dead _ slain judge Francisco Querol and his chauffeur, Armando Medina _ for a funeral Mass in one of the court's chambers.

The funeral for the third victim of Monday's blast, the judge's police bodyguard, Jesus Escudero Garcia, was held Tuesday in the southern city of Granada.

Twelve of those injured remained in Madrid hospitals Tuesday. One, a city bus driver, was in serious condition.

The bomb blew the judge's car over a bus and onto a sidewalk, setting vehicles ablaze and smashing windows in about 500 apartments and shops.

All political parties condemned the attack except the Basque independence group linked to ETA. The group said the bomb showed that negotiations must take place to resolve the region's conflict.

Monday's attack was the deadliest attributed to ETA since the organization ended a 14-month unilateral cease-fire last December. It is now blamed for 19 killings in 10 months, six in October alone.

Aznar, who survived an ETA assassination attempt in 1995, urged Spaniards not to despair over the continuing violence. On Monday, he repeated his refusal to engage in talks and pledged to fight ETA through police measures.

``It is clear that no one will achieve any kind of objective through the force of violence, and that no one will make Spaniards yield to threats of guns, whoever may be holding them,'' he said.