RAFAH, Gaza Strip (AP) – Israeli warplanes buzzed the seaside home of Syria’s president and bombed Hamas targets in Gaza on Wednesday to pressure Palestinian militants to free a kidnapped Israeli soldier.

Fighter jets also knocked out electricity and water supplies for most of the 1.3 million residents of the Gaza Strip. Three bridges were destroyed to keep militants from moving Cpl. Gilad Shalit, 19, who was taken hostage Sunday by three Hamas-affiliated groups.

Israeli military officials said on condition of anonymity that warplanes flew low over the home of Syrian President Bashar Assad because he has sheltered Hamas leaders blamed by Israel for masterminding the kidnapping.

No casualties have been reported since the offensive began early Wednesday. The army sent tanks and thousands of troops into Gaza.

The Hamas-led Palestinian government called for a prisoner swap with Israel, saying the offensive would not secure the soldier’s release. Hamas-affiliated militants holding the hostage previously made that demand, but this was the first time the government did.

Tensions escalated Wednesday evening as the military fired artillery near Gaza City _ the first time Israel has targeted that area during the offensive. The army said it was testing artillery units and not firing at specific targets.

Palestinians dug in behind walls and embankments as warplanes launched missiles in northern and southern Gaza.

Residents of northern Gaza, preparing for what they feared could be a long military operation, stocked up on food, candles and batteries for radios as a minister warned of a “humanitarian crisis.”

The White House continued pressuring Hamas, saying it was the responsibility of the Palestinian government to “stop all acts of violence and terror.” But the United States also urged Israel to show restraint.

“In any actions the government of Israel may undertake, the United States urges that it ensures that innocent civilians are not harmed, and also that it avoid the unnecessary destruction of property and infrastructure,” White House press secretary Tony Snow said.

It was Israel’s first ground offensive since pulling its soldiers and settlers out of Gaza last summer. Israeli Prime Minister Ehud Olmert said Israel would not balk at “extreme action” to bring Shalit home but did not intend to reoccupy Gaza.

Palestinian President Mahmoud Abbas deplored the incursion as a “crime against humanity,” and a leading Hamas politician issued a call to arms against the Israeli troops.

Meanwhile, concerns about the fate of a missing West Bank settler grew after militants claiming to hold him displayed what they said was a copy of his identification card.

Also, a group affiliated with Abbas’ Fatah party claimed to hold a third Israeli and threatened to attack an unspecified Israeli embassy within days.

Israeli tanks and soldiers began taking up positions east of Rafah overnight under cover of tank shells, witnesses and Palestinian security officials said. Capt. Jacob Dallal, a military spokesman, said troops moved a mile inside the coastal strip and were prepared for a long operation.

“Everything is on the table,” he said.

Fighter jets fired at least nine missiles at Gaza’s only power station, cutting electricity to 65 percent of the area, plant engineers said. The station’s three functioning turbines and a gasoline reservoir were engulfed in flames.

Wasfi Kabha, the Palestinian minister of prisoner affairs, said Israel was creating a “humanitarian crisis.”

“They hit the bridges, they hit the power station, so there will be a problem in water supply and health services,” he told the British Broadcasting Corp.

Areas in northern Gaza that receive electricity from Israel still had power, and some southern areas were able to get power from neighboring Egypt. Generators relieved darkness in other places.

The Israeli military said three bridges were attacked “to impair the ability of the terrorists to transfer the kidnapped soldier.” Knocking down the bridges cut Gaza in two, Palestinian security officials said.

Witnesses reported heavy artillery shelling near the long-closed Gaza airport outside Rafah. Warplanes flew low over the strip, rocking it with sonic booms and shattering windows.

Jets repeatedly fired missiles at open fields in Gaza, the military said. Two missiles hit empty Hamas training camps, witnesses said. Separately, Israel attacked a rocket-making factory in the area.

“We won’t hesitate to carry out extreme action to bring Gilad back to his family,” Olmert said. “All the military activity that started overnight will continue in the coming days.

“We do not intend to reoccupy Gaza. We have one objective, and that is to bring Gilad home.”

The militants who seized Shalit have demanded the release of hundreds of Palestinian women and children held in Israeli jails in exchange for information about him.

Olmert repeated that Israel will not negotiate with militants.

Later, the Palestinian Information Ministry said it was “natural logic” to carry out a prisoner exchange.

“Previous Israeli governments have done so … and this is what other countries do in conflict situations,” the statement said.

High-ranking Hamas officials in exile also demanded a prisoner exchange. If Israelis do not negotiate a swap, Palestinians militants will conclude “that they should capture more soldiers,” Hamas’ representative in Lebanon, Osama Hamdan, told The Associated Press.

Shalit was captured when militants tunneled under a Gaza crossing and killed two other soldiers at a military post. Israel believes the group’s Syria-based leaders ordered the operation.

Israeli Justice Minister Haim Ramon said Hamas’ Syria-based political chief, Khaled Mashaal, was “not immune” from Israeli reprisal.

“Khaled Mashaal, as someone who is overseeing, actually commanding the terror acts, is definitely a target,” Ramon told Army Radio. The station interpreted his comments as meaning Mashaal was a target for assassination.

Israel tried to poison Mashaal in Jordan in 1997. But Mossad agents were caught and King Hussein forced Israel to provide the antidote in exchange for their release.

Israeli fighter jets also flew over Assad’s summer home in an overnight raid near the Mediterranean city of Latakia in northwestern Syria, military officials said. Israeli TV said four planes were involved in the low-altitude flight, and Assad was there.

The flight caused “noise” on the ground, the military officials said on condition of anonymity, according to military guidelines.

The officials said Assad was targeted because of the “direct link” between Syria and Hamas.

Syria said its air defenses fired at the jets, forcing them to flee.

Abbas deplored the Israeli invasion, calling it “collective punishment and a crime against humanity,” and he urged the United States and other international negotiators to intervene, according to a statement.

An aide said Abbas called Assad to ask him to persuade Mashaal to free the soldier. Assad promised to do so, the aide said on condition of anonymity because he was discussing private talks.

Deputy Prime Minister Nasser Shaer of Hamas said his government, too, was trying to resolve the situation diplomatically.

The normally bustling streets of southern Gaza were eerily deserted, with people taking refuge inside their homes. The Rafah crossing between Gaza and Egypt _ Gaza’s main link to the outside world _ has been closed since Sunday.

Dozens of people living near the airport left their homes, seeking sanctuary in nearby Rafah. A small grocery nearby was open, but there were no customers.

Shalit’s abduction threatened to turn devastated relations between Israel and the Hamas-led government into all-out war. Hamas took over the Palestinian Authority after winning parliamentary elections in January and has been under international pressure to renounce violence and recognize Israel.

Complicating matters was a new claim by the Popular Resistance Committees, one of the three groups that carried out Sunday’s assault, that it also kidnapped Jewish settler Eliahu Asheri, 18, in the West Bank.

Outside a Gaza City mosque, PRC militants displayed what they said was a copy of Asheri’s ID card and reiterated threats to kill him if Israel did not end the invasion.

The group also warned that it had just begun its campaign to seize soldiers.

“The operation of kidnapping soldiers has started and is in a countdown,” spokesman Mohammed Abdel Al said.

Separately, a statement obtained by the AP and signed by Abu Fouad, spokesman for the Al Aqsa Martyrs’ Brigades in Gaza, said the group was holding an unidentified 62-year-old Israeli from Rishon Lezion.

The statement said the man was kidnapped Monday and that more evidence would be released later.

Israeli police spokesman Micky Rosenfeld said police had a missing persons report concerning a man named Noah Moskovitch.

In a separate statement, Al Aqsa said it planned to attack an unspecified Israeli embassy soon.