There are growing concerns Israel may soon unleash a punitive operation against the Hamas-ruled Gaza Strip after the military reported a dramatic increase in rocket attacks in January.

Prime Minister Binyamin Netanyahu has warned Hamas, which seized control of the densely populated coastal strip on Israel's southern border in June 2007, that Israel will teach it a lesson "very soon" if the attacks continue.

Intelligence Minister Yuval Steinitz threatened to invade Gaza, for the third time since December 2008 and topple the Hamas government.

Analyst Amos Harel told Haaretz since Israel unilaterally withdrew from Gaza, captured in the 1967 war, in 2005 "a rule of thumb of sorts was created making it possible to identify when rounds of hostilities would erupt ... based on the numbers of rockets fired from the territory.

"From the moment the pace returns to one a day, the countdown begins toward the next round of fighting."

Tension on the Gaza-Israel border has heightened in the last month after more than a year of relative calm following the last serious confrontation with Hamas and its unruly allies in late 2012.

"It appears ... a major escalation of the type seen in Operation Pillar of Defense in November 2012 is not far down the road," Harel observed.

Pillar of Defense occurred Nov. 14-21, 2012, and was launched after intense rocket fire by Hamas. The Israeli air force said it hit 1,500 Hamas targets in a ferocious campaign.

Gaza authorities reported 133 Palestinians were killed, 79 of them militants. Israeli losses were two killed amid an intense bombardment by Hamas and its allies in which 1,456 rockets were fired against Israeli cities.

That fighting paled against Operation Cast Lead, launched by the Israelis three years earlier. It began with a massive air assault and ground invasion Dec. 27, 2008, after heavy rocket bombardment from Gaza.

When the Israelis withdrew Jan. 18, 2009, under intense international pressure, about 1,400 Palestinians, mostly civilians, had been killed by U.N. count. Israel's losses were 14 killed, four by friendly fire. Both sides were accused of committing war crimes.

Amid the rising tension, the Times of Israel reported the fundamentalist Hamas' military wing has withdrawn most of the 900-strong force it had deployed there in a bid to maintain the 2012 truce by preventing militants firing rockets into southern Israel.

Defense analyst Avi Issacharoff noted in the Times of Israel Hamas' move "is likely to be interpreted as a green light to fire on Israel by the various terror groups in Gaza."

For reasons that have not been spelled out, Hamas withdrew its rocket-prevention force Saturday. There have been no rocket attacks since then.

But the Israeli army reported a sharp increase in attacks from Gaza throughout January. It said 14 rockets hit southern Israel, with five more intercepted heading for the port city of Ashkelon by the Iron Dome missile defense system designed to counter short-range rockets.

The Israelis have retaliated with airstrikes against launch sites and the militant units carrying out the attacks. Three airstrikes Friday hit a rocket storage depot and a makeshift factory where the weapons are manufactured in northern Gaza.

Earlier in January, the air force killed Palestinian militants Ahmed Saad and Ahmed Za'anin, who the Israelis allege were "extensively involved" in the planning and execution of rockets attacks as well as strikes against Israeli troops.

These days, militant attacks from Gaza are much more sporadic than in the recent past, largely because of Israel's retaliatory operations that are clearly based on high-grade intelligence from electronic surveillance and probably agents inside Gaza.

Hamas' political leadership appears committed to maintaining the cease-fire, as the deployment of the prevention force would indicate.

But analysts say the movement cannot control ultra-militant elements in Gaza, including jihadists who are becoming increasingly active in attacking Israel amid a worrying region-wide offensive from Iraq to Tunisia.

They infiltrate Gaza mainly from the lawless wastes of the Sinai Peninsula west of the Strip.

These forces appeared to be responsible for most of the recent violence, including a Grad rocket attack Friday on the resort city of Eilat on the Gulf of Aqaba that was claimed by the dominant jihadist group in Sinai, Ansar Bayt al-Maqdis, or Champions of Jerusalem.