Islamist group Hamas says it has brokered a deal for Gaza's militant groups to stop firing on Israel, amid the most serious fighting since 2009.
The move comes after militants hit an Israeli school bus with an anti-tank shell on Thursday, injuring two people.
Israeli strikes later that day had killed five people and injured more than 30, Palestinian doctors said.
And on Friday, two Hamas men had been killed by an air strike shortly after dawn, the group said in a statement.
Another four Palestinians were injured overnight in separate Israeli attacks at Rafah airport, according to Palestinian sources.
Israel says it is responding to Palestinian attacks.
Earlier, Israel said it had used a new short-range missile defence system for the first time to destroy rockets fired from Gaza.
The Iron Dome system had successfully intercepted a rocket heading for the southern port city of Ashkelon, the military said.
Last night, Hamas - which governs the Gaza Strip - met with other militant factions and agreed to enforce a ceasefire if Israel also stopped firing. The Hamas Interior Ministry said the truce was designed to stop an escalation of Israeli "aggression".
Friday's strike means that is unlikely to hold, says the BBC's Jon Donnison in Gaza City.
The past month has seen the most serious violence in and around Gaza since Israel's major offensive here more than two years ago, our correspondent adds.
On Thursday an Israeli teenager was critically injured near the Nahal Oz kibbutz when a school bus was targeted by a missile fired by Hamas militants.
The 16-year-old boy suffered a serious head wound and was taken to hospital for surgery.
After the attack, witnesses said more rockets and mortars were fired from the Gaza Strip.
The bus attack was condemned by the US, which said it was particularly concerned by reports that the Gaza militants had used an advanced anti-tank weapon to target civilians.
Following the attacks, Israeli planes bombed a compound in northern Gaza belonging to Hamas, along with targets in Gaza City and Rafah.
An official in Gaza said one of those killed on Thursday was a 50-year-old civilian who had been sitting outside his home when he was struck by tank fire. The other four were identified as leaders of the al-Qassam Brigades, the military wing of Hamas.
Friday's two victims had also been members of the al-Qassam Brigades, Hamas said. The men were killed in a dawn raid near the southern city of Khan Younis.
Another 40 Palestinians have been wounded by Israeli strikes in the past two days.
Israeli Prime Minister Benjamin Netanyahu said Israel would take any action necessary to deter attacks from Gaza.
"We hope this situation will be contained but we will not shy away from taking all the necessary action, offensive and defensive, to protect our country and to protect our citizens," said Mr Netanyahu during a visit to Prague.
Last month saw some of the worst violence since Israel launched a major offensive in Gaza in December 2008.
In one week in March, at least 10 Palestinians - including several civilians and children - were killed by Israeli attacks.
In the same period, militants in Gaza fired more than 80 rockets and mortar shells into southern Israel.
Israel says it holds Hamas responsible for all attacks coming out of Palestinian territory, even if it is other militant groups carrying them out.