The Basque group ETA claimed responsibility for a powerful car bombing that killed two people, and the Spanish prime minister postponed a trip to Japan next week in order to address lawmakers on the conflict with the separatists, a spokesman said. ETA, in a statement sent to the pro-independence newspaper Gara, said the fatalities in the Dec. 30 bombing had been unintentional, and insisted that a "permanent" cease-fire it called in March remained in force. The separatist group blamed the Spanish government for hindering a peace process launched with the ETA truce announcement, and said ETA reserved the right to respond if the government kept up "aggression" against the pro-independence movement. The bombing Dec. 30 destroyed a five-story parking garage at Madrid international airport, killed two men sleeping in parked cars and injured 26 people. The bombing also shattered a nine-month ETA cease-fire that Europe's last armed political militancy had called permanent.