The Middle East Quartet on Saturday expressed concern about the "unsustainable situation" in Gaza and warned of "the risk of escalation" while urging all sides to exercise restraint, DPA reported.
The Quartet, which comprises the United Nations, European Union, United States and Russia, condemned the attacks in southern Israel on Thursday as "cowardly acts of premeditated terrorism."
At least 15 people have been killed and 45 wounded, according to Palestinian sources, in the airstrikes on Gaza that began late Thursday, hours after a series of coordinated attacks in southern Israel.
Israel blames Palestinian militants for the attacks around the city of Eilat, in which eight Israelis were killed and 31 wounded.
In its statement, the Quartet expressed concern about the security situation in the Sinai Peninsula and encouraged the Egyptian government "to find a lasting resolution to the issue of Sinai security."
Israeli Defence Minister Ehud Barak on Saturday said he "regrets" the killings of five Egyptian policemen near the Israeli border, after Egypt threatened to recall its ambassador.