GAZA CITY, Gaza Strip - Palestinian militants targeted densely populated Tel Aviv in Israel's heartland with rockets for the first time Thursday, part of an unprecedented barrage that threatened to provoke an Israeli ground assault on Gaza. Three Israelis were killed in a separate rocket attack in southern Israel.
Air raid sirens wailed and panicked residents ran for cover in Tel Aviv, Israel's commercial and cultural capital. Israel responded by moving troops and heavy weapons toward Gaza and authorizing the call-up of tens of thousands of reservists.
There was no word on where the two rockets aimed at Tel Aviv landed, raising the possibility they fell into the Mediterranean. A third rocket landed in an open area on the southern outskirts of Tel Aviv.
Smoke rises following an Israeli attack on Gaza City, Thursday. Israel barraged the Gaza Strip with airstrikes and shelling Wednesday and killed the Hamas military chief in a targeted strike, launching a campaign aimed at stopping rocket attacks from Islamic militants. The assault killed 10 other Palestinians, including two children and seven militants. On Thursday, militant rockets fired into Israel killed three Israelis, raising the likelihood of a further escalation.
The fighting, the heaviest in four years, came after Israel launched a ferocious air assault Wednesday to stop repeated rocket fire from Gaza. The powerful Hamas military chief was killed in that strike, and another 18 Palestinians have died over two days, including five children. Some 100 Palestinians have been wounded.
Israeli warplanes struck dozens of Hamas-linked targets in Gaza on Thursday, sending loud booms echoing across the narrow Mediterranean coastal strip at regular intervals, followed by gray columns of smoke. After nightfall, several explosions shook Gaza City several minutes apart, a sign the strikes were not letting up, and the military said the targets were about 70 underground rocket-launching sites.
Israeli Prime Minister Benjamin Netanyahu said the army was hitting Hamas hard with what he called surgical strikes, and warned of a "significant widening" of the Gaza operation. Israel will "continue to take whatever action is necessary to defend our people," said Netanyahu, who is up for re-election in January.
There were mounting signs of a ground operation. At least 12 trucks were seen transporting tanks and armored personnel carriers toward Gaza late Thursday, and a number of buses carrying soldiers arrived. Israeli TV stations said a Gaza incursion was expected on Friday, though military officials said no decision had been made.
Defense Minister Ehud Barak said he authorized the call-up of reservists, and the army said up to 30,000 additional troops could be drafted.
"We will continue the attacks and we will increase the attacks, and I believe we will obtain our objectives," said Lt. Gen. Benny Gantz, Israel's military chief.
Hamas, meanwhile, warned it would strike deeper inside Israel with Iranian-made Fajr-5 rockets, acknowledging for the first time it has such longer-range weapons capable of hitting targets some 47 miles (75 kilometers) away. Tel Aviv is 40 miles (70 kilometers) from Gaza.
By nightfall Thursday, Hamas said it had fired more than 350 rockets into Israel. Israel, which estimates Gaza militants have as many as 12,000 rockets, said some 220 rockets struck the Jewish state and another 130 were intercepted by an anti-missile shield.
Israel believes Hamas has significantly boosted its arsenal since the last Gaza war four years ago, including with weapons from Iran and from Libyan stockpiles plundered after the 2011 fall of the regime there.
"After four years, we became stronger, we have a strategy and we became united with all the military wings in Gaza," said Hamas spokesman Fawzi Barhoum, referring to Hamas' setbacks during Israel's last major offensive in late 2008.