Rocket fire from Gaza to the Israeli side of the border increased Friday and struck residential areas in Ashdod, witnesses said.
One woman was slightly injured in Ashdod and several people suffered from shock, Haaretz reported.
At least 20 Palestinians and three Israelis have died since Israel began its offensive in Gaza Wednesday.
Israeli military officials said they were preparing for the possibility of using ground forces against militants in Gaza, Haaretz said.
British Foreign Secretary William Hague said on the BBC, "Israel does have to bear in mind that it is when ground invasions have taken place in previous conflicts that they have lost international support and a great deal of sympathy around the world."
Since Wednesday, 550 rockets had been fired toward Israel and 26 went off in developed areas, Israeli officials said. By noon Friday, the Iron Dome missile defense system had intercepted 109 rockets, they said.
The military's general staff approved the initial draft of 16,000 army reservists Friday. The government has approved the drafting of up to 30,000 people.
Israel's forces have hit more than 500 targets in Gaza, officials said.
Since Operation Pillar of Defense began with the killing of Hamas military leader Ahmed al-Jabari, Israel has hit most of the Fajr rocket-launching sites in Gaza, officials said. The Iranian-made Fajr rockets, when fired from the northern Gaza, can reach cities in central Israel.
Earlier Friday, rockets fired toward Ashkelon, Gan Yavne, and Be'er Sheva wounding three Israeli soldiers, Haaretz said.
The European Union's minister of foreign affairs, Catherine Ashton, said in a statement, "I am deeply concerned at the escalating violence in Israel and the Gaza Strip and deplore the loss of civilian lives on both sides."
Rocket attacks by Hamas and other militants in Gaza "which began this current crisis are totally unacceptable for any government and must stop," Ashton said.
"Israel has the right to protect its population from these kinds of attacks," she said. "I urge Israel to ensure that its response is proportionate."
Egyptian Prime Minister Hisham Qandil said Friday he witnessed "a disaster" in Gaza after Israel began its attacks against rocket-firing militants. Qandil visited the Council of Ministers building and a hospital in the city of Gaza, the BBC said
"What I am witnessing in Gaza is a disaster and I can't keep quiet. The Israeli aggression must stop," he said.
Qandil, who met with members of Hamas, which has governed Gaza since 2007, said Egypt would "spare no effort" to try to broker a cease-fire.
"Egypt is not planning to get the Palestinians to escalate; we are supporting them, but we don't want them to escalate," one official told Ahram Online. "On the contrary, we want a truce as soon as possible."
Qandil is a member of the Muslim Brotherhood, of which Hamas is an offshoot.
Officials unlocked air-raid shelters in Tel Aviv Friday, after residents took cover the day before following alerts of a missile threat, the BBC said.
Israel said two missiles had landed near Tel Aviv, one hitting an uninhabited area and another was thought to have landed at sea.
It was the first attempted attack on Tel Aviv since the Gulf War in 1991. Israeli officials earlier said a strike against Tel Aviv would be a "red line" that could trigger a ground war.
During a meeting scheduled for Saturday in Cairo, Arab League leaders are expected to condemn the Israeli operation and call on the international community to act to stop it, Ahram Online said.
In Washington, Obama administration officials said they asked friendly Arab countries with ties to Hamas, which Washington and Jerusalem regard as a terrorist group, to use their influence to seek a way to defuse the hostilities.
State Department spokesman Mark Toner, however, repeated the U.S. position that Israel has a right to defend itself from Palestinian rocket fire and said the "onus was on Hamas" to stop it.
U.N. Secretary-General Ban Ki-moon plans to visit Jerusalem, Cairo and Ramallah, the West Bank headquarters of the Palestinian Authority, Tuesday, the United Nations said.
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