Many buildings belonging to Hamas had been evacuated ahead of the strikes
At least 17 people have been injured by a series of Israeli air strikes in the Gaza Strip, Palestinian medics say.
There were reports of up to nine explosions in Gaza City, and in the north and south of the territory.
Witnesses say militant training camps operated by Hamas were targeted, as well as a workshop and cement factory.
On Saturday, Palestinian militants fired dozens of mortars into southern Israel in what was reportedly their heaviest such barrage in two years.
Among those wounded in Monday's air strikes were seven children, Palestinian medical officials said.
The BBC's Jon Donnison in Gaza City says warplanes could be heard over the Gaza Strip for more than an hour.
Many buildings belonging to Hamas, the Islamist group that controls Gaza, had been evacuated in anticipation of strikes, he says.
Air strikes in Gaza are not uncommon, but this seems to be one of the heaviest since Israel's major military offensive between December 2008 and January 2009, our correspondent adds.
More than 1,300 Palestinians as well as 13 Israelis were killed
