Israeli aircraft hit Gaza on Saturday for the first time since an August truce ended a 50-day war after a rocket hit the Jewish state, witnesses and the army said.
A Palestinian health ministry spokesman in the Gaza Strip said there were no casualties in the air strike, which came just hours after the rocket hit an open field in southern Israel on Friday without causing casualties or damage.
It was only the third time a rocket had been fired from the Palestinian enclave since the August 26 truce between Israel and Palestinian Islamist movement Hamas, the territory's de facto rulers.
The Israeli army said the air strike in the southern Gaza Strip had "targeted a Hamas terror infrastructure site".
Defence Minister Moshe Yaalon said the target was a concrete factory being used to repair tunnels in and out of Gaza, dozens of which Israel destroyed during the summer campaign.
The attack was "an unequivocal message to Hamas that we will not tolerate a return to a routine of sporadic firing at our citizens," Yaalon said.
Hamas did not say it was behind the rocket attack, but Israel holds it accountable for any rocket fire from Gaza.
"We hold Hamas responsible for what happens in Gaza, and will act forcefully against it if it won't prevent attacks at Israel," Yaalon said.
Gaza's Hamas leader Ismail Haniya condemned Israel's "dangerous violation of the ceasefire", and in remarks to reporters urged Egypt to "move with urgency" to ensure the Jewish state respects the agreement.
The summer war between Israel and Hamas killed almost 2,200 Palestinians, most of them civilians, and 73 people on the Israeli side, nearly all of them soldiers.
The Egypt-brokered ceasefire was to have been followed by talks on a more lasting truce, but these were called off amid deteriorating ties between Cairo and Hamas.
When the ceasefire came into effect, Prime Minister Benjamin Netanyahu vowed his government would not tolerate a single rocket being fired at Israel, and would strike back even more strongly if attacked.
Also on Saturday, the navy fired warning shots after fishing boats sailed beyond the six nautical mile limit enforced by Israel off Gaza's coast.
A military spokeswoman told AFP the vessels returned to waters where the navy allows them to operate.
