At the same time, the Israeli military has stepped up its offensive in the Hamas-controlled Gaza Strip.
The three Israelis died when a Hamas rocket hit a building in Kiryat Malachi, 25 kilometers north of Gaza.
The Israeli Army said its missile interceptor system -- the Iron Dome -- shot down dozens of the rockets fired from Gaza early on November 15 but that one got through and scored a direct hit on an apartment building.
"There was a direct strike on the upper part of the building," Israeli police spokesman Mickey Rosenfeld told the BBC. "Unfortunately, there was a family, a couple, that were in one apartment and then in the adjacent apartment next door there was also a woman. It took a direct strike. They didn't have enough time to get into a safety zone, a safety area, within the 30 seconds until the rockets landed and all three of them were killed."
They were the first Israeli fatalities since the military launched an operation on November 14 codenamed Pillar of Defense in response to Hamas rocket attacks.
During the operation, Israel killed the Hamas military chief, Ahmed Al-Jaabari, and bombarded Gaza from the land, sea, and air, killing 13 people, including two children.
Avital Leibovich, an Israeli Army spokeswoman, said the current operation could be extended.
"All the options are on the table, including the possibility of a ground operation," Leibovich said. "We have alerted some of our reserve units and we are considering our next steps. Currently, we are striking various targets from the air, targets of either caches of rockets, storages of rockets, underground tunnels used to store rockets, and other targets."
Saeb Erekat, a senior Palestinian Authority official, speaking in Geneva, said the operation has prompted President Mahmud Abbas to cut short a European trip.
"The escalation in the Gaza Strip -- the Israeli aggression against Gaza -- for this President [of the Palestinian Authority Mahmud] Abbas decided to cut short his visit to Europe immediately after he finishes his next two meetings in Switzerland with the [Swiss] president and the speaker," Erekat said. "He will be returning back home to follow the situation immediately. We have a very grave situation in Gaza."
The Palestinian Authority lost control of Gaza to Hamas in 2007 and now rules only in the West Bank. However, Abbas claims to be president of all Palestinians.
Egyptian President Muhammad Morsi said in televised remarks on November 15 that Israel's "aggression" was "unacceptable."
Morsi said Cairo has protested to Israel through dipomatic channels.
"Our position yesterday was clear, and we expressed our position by withdrawing the Egyptian ambassador from Israel and recalled the Israeli ambassador to deliver to him a message through the Foreign Ministry on our position on the aggression against Gaza," Morsi said.
Morsi also said he has talked to U.S. President Barack Obama and UN chief Ban Ki-moon about the situation.
Meanwhile, Russia expressed concern about the developments and said the escalation of the violence was "impermissible."
British Foreign Secretary William Hague called for restraint, but added that "the prime responsibility" for the crisis lies with Hamas.