Palestinian Authority President Mahmoud Abbas, who heads the rival Fattah Party, called for an end to the bombing, Voice of America reported.

Amr Moussa, secretary-general of the Arab League, said the bombing was "an unimaginable and unacceptable act."

But a spokesman for U.S. President George Bush put the onus on Hamas, the Kuwaiti news agency KUNA reported. Gordon Johndroe said the president would like Israel to take more care to safeguard civilians.

"Hamas's continued rocket attacks into Israel must cease if the violence is to stop. Hamas must end its terrorist activities if it wishes to play a role in the future of the Palestinian people," Johndroe said.

France, speaking as president of the European Union, deplored "the escalation of violence in the Gaza Strip." The statement from Brussels condemned both Hamas for firing rockets from Gaza and Israel for its "disproportionate use of force."

Egyptian President Honsmi Mubarak said medical care would be available for Palestinians injured by the bombings, and that they would be admitted through the Rafah Crossing. Parliamentary leaders and Cabinet members called for an end to Israeli "aggression."

U.N. Secretary-General Ban Ki-moon was said to be "deeply alarmed" by the violence by both sides.

"He appeals for an immediate halt to all violence," a spokesman for Ban said in a statement released at the United Nations in New York.