An Israeli helicopter gunship fired missiles on the building housing the offices of Palestinian Prime Minister Ismail Haniya in Gaza City early Sunday, setting the structure ablaze.
Hours later, Israeli Interior Minister Roni Bar-On told Israel Army Radio that Israel was "tightening the pressure on Hamas."
A bystander to the missile strike suffered minor injuries, hospital officials said. No other casualties were reported. Palestinian sources said the airstrike set the building ablaze.
The missile strike in Gaza City was confirmed by Israel, which launched expansive assaults on Gaza after Palestinians kidnapped Israeli army Cpl. Gilad Shalit, 19, on June 25.
Israeli sources said Haniya's office was being used by terrorists to plan attacks.
Outside the office early Sunday, there was mayhem, as flashing lights from emergency vehicles illuminated the building and scores of anxious Palestinians surveyed the scene.
As Haniya joined them, he said the attack was the product of "barbaric politics."
"This is a part of targeting the Palestinian people, who suffer such strikes in the West Bank and Gaza Strip. It is obvious that logic has been lost," Haniya said.
"The Palestinian issue is bigger than any senior position or ministry. Therefore, we plan to continue our commitment to the government and our responsibilities, God willing."(Watch as Palestinians struggle without basic necessities -- 2:45)
Israel launched two more airstrikes within an hour of the attack on Haniya's office, both in or near the Jabaliya refugee camp in Gaza, Palestinian sources said.
The attacks were on an open field used as a Hamas training ground and on a house that the Hamas militia uses as its headquarters, according to Israeli sources.
At least one person was killed in the attack on the house, Palestinian sources said.
The strikes followed reports by the Israel Defense Forces of clashes with Palestinian gunmen east of Khan Yunis, where Israeli intelligence officials say they suspect Shalit is being held.
The gunmen fired small arms at Israeli soldiers and an anti-tank missile at an engineering vehicle, the IDF said. The gunmen also planted explosive devices in the area.
The Israelis returned fire, but no casualties were reported, according to Palestinian security sources.
Humanitarian aid allowed into Gaza
In the midst of the standoff over Shalit, Israel opened two routes into Gaza on Sunday to allow for humanitarian aid to flow into the Palestinian territory, an Israeli army official said.
The Karni crossing in northern Gaza and a nearby fuel terminal at Nahal Oz were opened at midday to allow for the passage of food, medicine and fuel.
Israeli Defense Minister Amir Peretz said the Karni crossing would be open four days so trucks could carry humanitarian supplies into Gaza.
Meanwhile, diplomatic efforts continued in an effort to secure the release of Shalit.
The U.N. envoy to the Middle East, Alvero de Soto, was expected to meet Sunday with Palestinian Authority President Mahmoud Abbas in Gaza.
The Israeli military operations in southern Gaza and the West Bank include the arrests of several members of the Palestinian government. In a statement faxed to the media early Saturday, an Israeli Foreign Ministry spokesman repeated that Shalit must be freed without conditions.
"Prime Minister Ehud Olmert has reiterated that there will be no deals, that either Shalit will be released or we will act to bring about his release," Mark Regev said.
Egypt and Qatar have been working to broker a settlement, and Egyptian President Hosni Mubarak told the government newspaper al-Ahram late Thursday that the Palestinian ruling faction Hamas had approved a conditional plan for returning Shalit.
However, Mubarak said Israel rejected the terms. Israel contends that doing so would encourage more abductions.
On Saturday, a spokesman for Abbas said the president still hopes a negotiated solution can be reached. He denied that there were deadlocks in negotiations, as reported by some media.
Three Palestinian militant groups -- the militant wing of Hamas, the Palestinian ruling faction; the Popular Resistance Committees; and a previously unknown group, the Army of Islam -- have claimed responsibility for Shalit's abduction.
The groups faxed a statement to media outlets Saturday demanding the release of 1,000 Arab prisoners, including women and children, from Israeli jails.
The message did not specify if the new demand was in exchange for Shalit's freedom. (Full story)
On Saturday, a White House spokesperson said President Bush called Shalit's release key to ending the crisis between Israel and the Palestinians in Gaza.