(CNN) -- Israel responded with heavy fire after five rockets from Gaza landed Wednesday in populated areas of southern Israel, marking "the most substantial attack" in two years against the country, the Israeli military said.
The military wing of the Palestinian Islamic Jihad, called the Al-Quds Brigade, claimed responsibility for firing dozens of missiles on what it called "Israeli settlements."
In response, Israel launched airstrikes on three areas in Gaza -- Rafah, Khan Younis and Jabalia -- that are believed to belong to Islamic Jihad, according to security sources in Gaza. A Hamas spokesman texted CNN to say they counted six airstrikes, but claimed they were against bases that were empty.
In all, the Israeli military targeted "29 terror sites" in Gaza, the military said on its Twitter page.
"Direct hits were confirmed," the military tweeted.
"In today's attack, 41 rockets struck in Israel, five hit populated areas and three were intercepted by the Iron Dome defense system," the military said in another statement. "This is the most substantial rocket attack from the Gaza Strip since Operation Pillar of Defense in November 2012."
Islamic Jihad and Hamas, which is the Palestinian movement running Gaza, evacuated their military and civilian institutions on expectation of Israeli reprisals, the security sources in Gaza said.
In the wake of the attack, Israeli Foreign Minister Avigdor Liberman told Israeli army radio that "the position of my party Israel Beitanyu is that we support the full occupation of the whole of Gaza in any possible future action."
Liberman opposed a response short of full occupation. "I am against a limited operation," he said.
Israeli Prime Minister Benjamin Netanyahu was later asked for his reaction to Liberman's comments at a joint news conference with Britain's Prime Minister David Cameron Wednesday evening in Jerusalem.
"If it is not quiet in southern Israel, it will be very noisy in Gaza," Netanyahu said in Hebrew.
Palestinian Authority President Mahmoud Abbas has called upon Israel to stop the "military escalation on the besieged Gaza Strip, considering that this escalation will put the isolated residents in the danger of the war and destruction," presidential spokesman Nabil Abu Rudeineh said through the official Wafa news agency.
"The Gaza Strip is constantly being targeted by Israeli airstrikes that targeted many areas," Rudeineh said.
Hamas-run Al-Aqsa TV flashed a banner stating: "The occupation bares the full responsibility regarding this wave of aggression and the ongoing escalation."
Abu Ahmad, spokesman for the Al-Quds Brigades, said the rocket fire came "after a long series of violations to the truce with the Palestinian resistance since November 2012."
"This operation, dubbed 'Breaking the Silence,' comes as a response to the ongoing and continued Zionist Israeli aggression against the Palestinian people in the West Bank and Gaza," Ahmad said.
Israeli Defense Minister Moshe Yaalon ordered a halt to the shipment of goods to Gaza through a crossing on the Gaza-Israel-Egypt border until security assessments are made, the military said in statement.
However, another crossing will be open for humanitarian movements, the military said.
U.N. Secretary-General Ban Ki-moon condemned the multiple rocket attacks from Gaza on Israel and urged maximum restraint by all parties to prevent an escalation of violence and destabilization to the region, a spokesman said.
Israeli Apache helicopters flew over Gaza City on Wednesday after several rockets were reportedly fired from the Palestinian territory at the Israeli town of Sderot, officials said.
The Al-Quds Brigade claimed responsibility on its website for firing a total of 34 rockets and 14 mortar rounds at "Zionist targets."
CNN's Talal Abu Rahma in Gaza, Kareem Khadder in Jerusalem, Mohammed Tawfeeq and Michael Schwarz contributed to this report.