Israel launched half a dozen air strikes on the Gaza Strip on Thursday, killing at least one Palestinian and wounding another, medical workers and the Islamist group Hamas said.
The raids came on a day when a dozen mortar bombs and a rocket fired from the territory struck the Jewish state, although no injuries were reported inside Israel.
Explosions rocked Gaza City, Khan Younis and Rafah, which is on the Egyptian border, sending flames shooting into the air, Reuters reported.
The Israeli armed forces had no immediate comment but a security source, speaking on condition of anonymity, confirmed the air raids had been carried.
One Palestinian died and another was hurt in the latest Israeli raid on a tunnel beneath Gaza's border with Egypt, and several other people were feared trapped inside the ruins, medics said.
Israel says the subterranean passages are used to smuggle weapons from Egypt, while Palestinians say they need the tunnels to bring in staple supplies due to an Israeli blockade of the coastal Gaza territory.
Israel's first strike of the evening was its first inside the crowded city of Gaza since a three-week offensive a year ago in which 1,400 Palestinians and 13 Israelis were killed.
Israeli media reports said a weapons factory in Gaza City had been targeted.
Hamas, a militant group that rules Gaza, said an Israeli warplane bombed a building in Gaza City that witnesses said appeared to belong to the Islamic Jihad militant group. Militants barred reporters from reaching the area.
Israel also fired missiles at targets in Khan Younis, a town in southern Gaza. One of them struck an uninhabited area near a school, causing no injury, witnesses and medics said.
A further air strike targeted a zone in southern Gaza where militants of the Popular Resistance Committees fire mortars at Israel. The group claimed responsibility for shooting at Israel earlier, striking two days after Israel killed one of its commanders in an aerial raid in Gaza.
Israel dropped leaflets over Gaza on Thursday, warning many of its 1.5 million residents to avoid areas within 300 meters (yards) of the border fence with Israel.
The mortar bombs and rocket fired at Israel earlier on Thursday caused no casualties, an Israeli military spokesman said. The number of such attacks has risen in the past few weeks after months of relative calm since the Gaza war.