Israel will take "whatever action is necessary" to defend its citizens from Palestinian rocket attacks, Prime Minister Benjamin Netanyahu said on Thursday as Gaza's Hamas rulers noted that the current conflict “will shorten the era of occupation.”

Netanyahu's remarks at a televised press conference in Tel Aviv came after Israel carried out 24 hours of air strikes on Gaza, killing 15 Palestinians, at least seven of them Hamas militants.

Hundreds of Tunisians demonstrated on Thursday against Israel's deadly attacks on Gaza, as Israeli planes pounded armed groups in the Palestinian territory for a second day, an AFP journalist reported.

Several hundred protesters, gathered on Habib Bourguiba Avenue in the center of Tunis, shouted slogans such as "No to reconciliation," and "The people want to criminalize normalized relations with the (Zionist) entity."

Israel's air strikes on the Gaza Strip have heightened the tensions surrounding the Palestinian bid for observer membership at the United Nations planned for later this month.

The Palestinian U.N. envoy said Wednesday's attack -- which killed the top Hamas military commander in the territory -- was deliberately timed to torpedo the U.N. vote in two weeks and influence Israel's general election in January.

Israel will never defeat Gaza, Khaled Meshaal, the exiled chief of the Hamas movement which rules the Palestinian territory, said in a defiant speech in Sudan on Thursday.

"This enemy is weak and cannot vanquish Gaza," Meshaal told a major conference of Sudanese Islamists.

Former Prime Minister Saad Hariri slammed on Thursday the Israeli assault against the Gaza Strip, saying that it demonstrates the “hostile policy of Israel against the Palestinians and Arab people in general.”

He said in a statement: “The occurrence of the attack simultaneously with the ongoing Syrian revolution poses questions over its timing and is a sign of the clear intentions to thwart the revolt as much as possible.”

Iran's foreign ministry on Thursday condemned as "organized terrorism" a vast Israeli operation launched in the Gaza Strip.

Iran "strongly condemns the criminal act of Zionist (Israeli) military forces in killing civilians," ministry spokesman Ramin Mehmanparast said in remarks published on the website of state broadcaster IRIB.

Gunfire from Syria hit the Israeli-occupied Golan Heights on Thursday morning, the Israeli military said, in the latest spillover of violence from the bloody civil war raging across the ceasefire line.

"Stray bullets fired in Syria reached Israel. No soldiers were injured by the gunfire," a spokeswoman said.

Egypt's President Mohammed Morsi rejected on Thursday what he called Israel's aggression in Gaza, saying it threatened to destabilize the region, while Cairo called on the US to stop Israel's strikes.

"The Israelis must understand that we do not accept this aggression, which can only lead to instability in the region," Morsi said in televised remarks, as Israeli air forces pummeled Gaza and militants fired rockets back in a deadly tit for tat.

President Michel Suleiman reiterated on Thursday calls for international pressure on Israel to engage in peace talks with Palestinians, saying war does not contribute to democracy in the region.

In a statement issued by Baabda palace, Suleiman condemned the “barbarous aggression launched on the Gaza (Strip) by Israel, which only uses the language of killing and destruction.”

U.N. chief Ban Ki-moon considered that there are deliberate attempts to destabilize the situation in Lebanon, expressing his “deep concern” over the possibility of the Syrian crisis spilling over into the country.

Ban stressed that the international community is determined to preserve stability in Lebanon, saying there should be no impunity in the October 19 assassination of Internal Security Forces Intelligence Bureau Chief Wissam al-Hasan.