Gaza City (CNN) -- A cease-fire didn't last very long Thursday as more than a dozen rockets from Gaza were fired at southern Israel and the Israeli air force hit what it labeled as seven terror sites, according to Israel Defense Forces.
Of the 18 rockets fired, eight struck Israel and eight landed in Palestinian areas, IDF tweeted. Two were shot down, Israel said.
Palestinian security officials told CNN that Israeli warplanes bombed a training base of al-Qassam Brigades -- the military wing of Hamas -- while another targeted an old intelligence building. There were no casualties, the officials reported.
IDF said it attacked four sites in the southern Gaza and three in northern Gaza.
"Militants attacking Israel from the Gaza Strip will not feel safe, will pay the price and will find that their actions are futile," Lt. Col. Peter Lerner, a spokesman for IDF, tweeted.
There was news earlier of an Egyptian-brokered truce. Islamic Jihad Khaled Al-Batash told CNN the truce started at 3 p.m. local (9 a.m. ET). Two hours later, two rockets were fired from Gaza, Israeli police spokesman Micky Rosenfeld said.
Palestinian leader blames Israel
Israelis have been preparing for continuing violence, with IDF calling up reservists to man Iron Dome batteries that are intended to intercept missiles from Gaza, according to a spokesman. They intercepted three such missiles Wednesday night and the two Thursday.
Another spokesman said the reserves were being brought in for "operational assessment and accordance with the air force necessities."
Islamic Jihad said the flare-up came after three of its operatives were killed Tuesday by an Israeli military strike in Gaza. The operatives had traveled to Gaza to inspect an Israeli drone -- a small surveillance aircraft -- that had become disabled, Islamic Jihad said.
Palestinian Authority President Mahmoud Abbas blamed the Israelis for the outbreak. "The Israeli occupation forces killed in cold blood three Palestinians in the West Bank and another three in Gaza, and we did not hear any condemnation or any apologies to these acts from the Israeli government," he said Thursday in a joint news conference in Bethlehem with British Prime Minister David Cameron.
"And, yesterday, the launching of rockets happened from Gaza and Israel retaliated to that, and we condemn this escalated military aggression in all its forms, including the firing of rockets," he told reporters, according to the Palestinian news agency WAFA.
Israeli Defense Minister Moshe Yaalon blamed the attacks on Hamas, which has governed Gaza since 2007, two years after Israel disengaged unilaterally from the area. "The Hamas is responsible for Gaza and if the Hamas does not know how to ensure the quiet, they will also be responsible," he said in Hebrew. "We are prepared for all possibilities."
Only a few days ago, Egypt declared Hamas a terrorist organization and outlawed its activities in the country. This followed the military-backed government's fierce crackdown on the Muslim Brotherhood, which is linked to Hamas.
Airstrikes, rocket fire
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.
Prime Minister Benjamin Netanyahu was asked Wednesday evening for his reaction to Liberman's comments at a joint news conference with Cameron in Jerusalem. "If it is not quiet in southern Israel, it will be very noisy in Gaza," Netanyahu said in Hebrew.
The announcement of the cease-fire came shortly after four Palestinian residents were critically wounded in an airstrike on tunnels near the southern Gaza city of Rafah, Palestinian medical sources told CNN.
A Hamas website reported five people were injured in two attacks.
Security sources said one of the attacks struck west of Rafah, destroying two tunnels; a second attack struck east of Rafah on open land.
Israel Defense Forces said that two rockets hit southern Israel Thursday and that the country's air force retaliated "by targeting seven terror sites" in southern Gaza.
Since Wednesday, about 65 rockets have struck Israeli territory, five of them hitting populated areas, IDF said.
Lerner said Thursday in a statement that there had been "a substantial deterioration" in the safety of southern Israel's residents. "We have responded and will continue to do so in order to eliminate threats as they develop. This is our obligation and responsibility to those exposed to Gaza terrorism."
CNN's Talal Abu Rahma reported from Gaza, Kareem Khadder from Jerusalem and Tom Watkins from Atlanta. CNN's Hamdi Alkhshali, Mike Martinez, Salma Abdelaziz, Mohammed Tawfeeq and Michael Schwartz contributed to this report.