Using U.S.-made aircraft and at least one bomb with U.S. markings, Israeli forces blasted Palestinian police structures in the Gaza Strip and West Bank on Sunday, responding to the killings of five Israelis a day earlier.

A Palestinian policeman was killed and 18 people injured when F-16 and F-15 warplanes dropped bombs on Palestinian police headquarters in Gaza City, Dir al-Balah in southern Gaza and the Salfit village in the West Bank on Sunday morning. In other violence Sunday, another Palestinian and an Israeli were also killed.

At a news conference, Palestinian spokeswoman Hanan Ashrawi charged that "Israel is using American weapons against human rights."

Responding, Israeli Public Security Minister Uzi Landau said: "I don't have to justify it. It's a clear move that you take in order to respond to acts of terror."

Israel usually targets Palestinian security installations in its retaliatory strikes because it holds Palestinian leader Yasser Arafat ultimately responsible for attacks on Israelis. Israel says Arafat's security forces do little to rein in the militants, and sometimes participate in attacks on Israelis.

The Palestinians blame Israel for the violence, charging that its occupation of the West Bank and Gaza Strip is the cause, exacerbated by roadblocks and travel restrictions there. The Palestinians say their police and security are defending themselves against Israeli aggression.

Now the Palestinians charge that the United States is blatantly taking Israel's side in the conflict.

On Sunday, Palestinian police officers inspected the ruins of the four-story building in Gaza City that housed their headquarters, showing reporters a green metal fragment with yellow lettering that said "for use on M-84" -- referring to a one-ton bomb that, according to the Pentagon's Web site, can be fitted with a laser guiding device and carried by the U.S.-made warplanes used in the raids.

The Israeli military said only that the bomb was not a new type and has been used before. The U.S. air force dropped thousands of M-84 bombs on Iraq in the 1991 Gulf War.

U.S.-made Israeli attack helicopters hovered near Arafat's headquarters during the air strike, but they did not open fire. Returning to Gaza on Sunday after a trip to Asia, Arafat briefly toured a police structure that was shelled by Israeli tanks in Rafah, near the Egyptian border.

Asked Sunday about the legality of Israel's use of U.S. weapons against the Palestinians, a State Department official expressed opposition to use of heavy weapons in urban areas, where the risk of casualties is high. Speaking on condition of anonymity, she said the State Department monitors the use of U.S. weapons to ensure they are used according to the terms of transfer under American law.

The law requires U.S. weapons to be used for security and self-defense. Israel's rivals have complained often about its use of American-made weapons, but the United States has not made a legal issue of the matter, preferring to deal with it on the political level.

Sunday marked the third time Israel has used warplanes against the Palestinians in the West Bank and Gaza Strip. The two other strikes came May 18 and Aug. 10, after Palestinian suicide bomb attacks in Israel.

Altogether, seven Israelis and four Palestinians were killed over the weekend, further dimming the already slim prospects that Arafat and Israeli Foreign Minister Shimon Peres might renew truce talks. They had agreed in principle to meet, but no date was set.

Each side blames the other for the fighting that broke out 11 months ago, and which has killed 588 people on the Palestinian side and 160 on the Israeli side.

After nightfall Sunday, Israeli helicopters attacked a Palestinian security base in the town of Tulkarem in what the military said was a direct response to the killing of an Israeli driver earlier in the day. No casualties were reported as a result of the helicopter raid.

Also, tanks shelled three Palestinian police checkpoints near the town of Ramallah, Palestinians said. Four Palestinians were wounded when a shell hit a house, they said. The Israeli military said the attacks were response to Palestinian roadside ambushes.

An Israeli wounded in a West Bank roadside shooting Saturday died of his wounds Sunday, Israeli media reported. Hospital officials were unavailable for comment. The shooting left an Israeli couple dead and their two small children lightly wounded.

Also Sunday, another Israeli driver was shot and killed by a Palestinian gunman along the border between the West Bank and northern Israel, Israeli police spokesman Gil Kleiman said. Police said the Israeli was killed while making a business transaction with a Palestinian. The Al Aqsa Brigade, affiliated with Arafat's Fatah movement, claimed responsibility in a leaflet faxed to The Associated Press; the group had also claimed Saturday's West Bank shooting.

In another incident, a Palestinian was killed in unclear circumstances near the fence between Gaza and Israel, Palestinians said. They said he was hit by a tank shell. The Israeli military had no comment.

On Saturday, two Palestinian militants infiltrated an Israeli army outpost in Gaza and killed three soldiers before being killed themselves.