GAZA CITY (CNN) -- Israel bombed a Hamas government compound early Tuesday, leveling at least three structures, including the foreign ministry building, eyewitnesses and Hamas security sources told CNN.



Relatives mourn three boys from the same family who were killed in an Israeli airstrike Monday in Gaza.



A Gaza-based journalist, whose name was withheld for security reasons, told CNN he heard 18 blasts in the area and that two fires were burning at the compound early Tuesday. More bombs continued to drop over Gaza through the morning.  With Tuesday's bombs, Israel appeared to extend its airstrike campaign in Gaza to a fourth day. The strikes -- which Israel says are aimed at stopping the firing of rockets from Gaza into southern Israel -- have killed more than 375 Palestinians, most of them Hamas militants, Palestinian medical sources said Tuesday.



At least 60 civilians have been killed in Gaza, U.N. officials said. About 650 people have been wounded there, according to the Palestinian medical sources.



Monday, Israel's defense minister said the nation was in an "all-out war" with Hamas, the Palestinian militant group that rules Gaza.



"We have stretched our hand in peace many times to the Palestinian people. We have nothing against the people of Gaza," Defense Minister Ehud Barak told Israel's parliament. "But this is an all-out war against Hamas and its branches."



Israel continues to strike Hamas targets in Gaza, an Israel Defense Forces spokesman told CNN.



Mortar fire along the Gaza border late Monday killed one Israeli soldier and wounded four others, he said.



Earlier Monday, columns of smoke rose over Gaza City as warplanes carried out strikes. Though there was no indication of an Israeli military ground operation in Gaza, Israeli tanks cruised along the territory's edges.  Watch rocket fire force a reporter to take cover »



Iyad Nasr, a spokesman for the International Committee of the Red Cross, said the streets of Gaza were largely empty during airstrikes Monday morning.



Despite the airstrikes, militants fired  more than 40 rockets and mortar shells into Israel on Monday, according to Israeli police spokesman Mickey Rosenfeld. More than 150 rockets have been launched into Israeli territory since the campaign began, Israel Defense Forces said.  Watch damage in Sderot »



Six Israelis have died over the past three days, five of them civilians.



One of the rocket strikes killed an Israeli at a construction site in Ashkelon, 6 miles (10 kilometers) north of Gaza, and wounded eight others, a hospital spokeswoman said. Rocket strikes killed an Israeli and wounded two others at Kibbutz Nahal Oz, according to Israeli police and hospital spokespersons.



Rocket attacks also wounded two people, one seriously, in Ashdod. One woman who was critically injured during the attack died later during an operation, according to Israeli medical sources.



The White House on Monday called on Hamas to halt rocket fire against Israel, so calm can be restored in Gaza.  Watch the White House blame Hamas »



Israel has struck more than 300 Hamas targets since Saturday, its military said. The Israeli air force carried out at least 20 airstrikes on Gaza on Monday, Israeli military sources said.



Hamas security sources said the targets included the homes of two commanders of Hamas' military wing, the Izzedine al-Qassam Brigades, in the Jabalya refugee camp just north of Gaza City. Neither commander was among the seven people killed in those strikes, the sources said.



The Israeli military had no immediate comment on a report by Dr. Mu'awiya Hassanein that a strike near a mosque in Jabalya killed five children in a nearby home.



The situation triggered protests in Iran, Greece, Britain and Lebanon, and the Iranian government declared a day of mourning for Palestinians in Gaza.



Iran's Supreme Leader Ayatollah Seyed Ali Khamenei urged the world's Muslim populations to unite against Israel's attacks on Hamas in Gaza.  Watch a demonstration in London »



"All true believers in the world of Islam and Palestinian fighters are duty-bound to defend the defenseless women and children in Gaza Strip and those giving their lives in carrying
Who declared a day of warning? Who declared a day of mourning? What did Barak think of the War? What did Tehran declare? What did Israeli bombs destroy? What was levelled by bombs?
the Iranian government Iranian government "We have stretched our hand in peace many times to the Palestinian people. We have nothing against the people of Gaza," "all-out war" Hamas government compound foreign ministry building,
question: Who declared a day of warning?, answer: the Iranian government | question: Who declared a day of mourning?, answer: Iranian government | question: What did Barak think of the War?, answer: "We have stretched our hand in peace many times to the Palestinian people. We have nothing against the people of Gaza," | question: What did Tehran declare?, answer: "all-out war" | question: What did Israeli bombs destroy?, answer: Hamas government compound | question: What was levelled by bombs?, answer: foreign ministry building,