“IDF air and ground troops are currently attacking in the Gaza Strip,” the tweet from Israel Defence Forces read.
“I said we would extract a very heavy price from Hamas,” Prime Minister Benjamin Netanyahu said in a videotaped statement earlier today.
“We are doing that, and we will continue to do that with heavy force.”
Hours earlier, Israel called up 7000 military reservists.
The fighting broke out late on Monday when Hamas, claiming to be the defender of Jerusalem, fired a barrage of long-range rockets toward the city in response to what it said were Israeli provocations.
Israel quickly responded with a series of airstrikes.
Since then, Israel has attacked hundreds of targets in Gaza.
The strikes set off scores of earth-shaking explosions across the densely populated territory.
Gaza militants have fired nearly 2000 rockets into Israel, bringing life in the southern part of the country to a standstill.
Several barrages targeted the seaside metropolis of Tel Aviv, some 70km away.
– Reported with Associated Press