Four people have died in an Israeli strike on a Hamas-run police station in the southern Gaza city of Khan Younis, Palestinians say.
The strike comes as Israel considers wider measures against Gaza
The Israeli military said in a statement it had targeted a rocket crew position in southern Gaza.
It said it attacked "in response to rocket and mortar attacks... on localities in southern Israel".
The strike came as Israeli Defence Minister Ehud Barak warned a "broad operation" was imminent in Gaza.
He told reporters: "Every passing day brings us closer to a broad operation in Gaza.
"We are not looking forward to it, we would be happy if circumstances prevented it."
Analysts say the army would face unprecedented resistance from Hamas militants who have been rearming and digging in in the densely populated territory.
Israel has carried out several air strikes inside Gaza in recent months in retaliation for almost daily rocket attacks on Israel by Palestinian militants.
The BBC's Aleem Maqbool in the West Bank says Israel's pressure on Hamas, or on the Gaza Strip, is not relenting.
Earlier on Tuesday an Israeli missile hit a house in northern Gaza, injuring two children.
The military said it was aiming at a rocket squad, but the missile misfired, hitting the house.
The Israeli attacks followed a mortar attack on an Israeli farming community near the border, causing damage to a house but no injuries.
Hamas seized control of the Gaza Strip in June, ousting its Fatah rivals.
On Monday Israel said it would reconsider plans to curb power supplies to Gaza, in retaliation for rocket attacks, after legal advice from the attorney general.
UN Secretary General Ban Ki-moon had condemned the plans as unacceptable and punitive.
Israel's Supreme Courts has given the government until Friday to justify the economic sanctions it is seeking to impose on the Palestinian territory.
Gaza relies on Israel for almost all its fuel and petrol, and more than half of its electricity.