The airstrikes, launched on Sunday, targeted tunnels used by Palestinian smugglers, a Hamas traffic control post and the border area between Gaza and Egypt. There are no reported casualties.
The latest violence threatens a fragile ceasefire imposed two weeks ago following a three-week Israeli offensive which saw some 1,300 Palestinians, mostly civilians, killed and more that 5,300 injured and caused widespread damage and destruction.
On early Sunday militants managed to launch rockets and mortars on southern Israel injuring two service personnel and one civilian.
At a government meeting on Sunday Prime Minister Ehud Olmert said, "If there is shooting at residents of the south, there will be an Israeli response that will be harsh and disproportionate by its nature."
Washington's new Middle East envoy has meanwhile called for the strengthening and extension of the current Gaza ceasefire between Israel and Hamas.
"It is of critical importance that the ceasefire be extended and consolidated," George Mitchell said.
The United Nations has launched an appeal for $613 million to help Gaza in the wake of Israel's military offensive. UN Secretary General Ban Ki-moon, who visited Gaza last month, said the region could face a greater humanitarian disaster if action was not taken immediately.
