The Israeli military is preparing for intensified strikes in the Gaza Strip against Palestinian militants who bombarded southern sections of Israel with around 150 rockets and mortar shells last weekend.

That's heightened fears that a rerun of the Israelis' highly controversial 22-day invasion of the Hamas-ruled coastal territory in December 2008. That deadly exercise raised a global whirlwind of criticism of the Jewish state.

"We will strike back with an ever-growing intensity," Israeli Defense Minister Ehud Barak, a former prime minister and military chief of staff," warned Sunday night.

"Over the last two days, the Israeli Defense Forces, on my instructions, has been evaluating a host of options for harsher responses against Hamas and the other terror organizations in Gaza."

Israeli Prime Minister Binyamin Netanyahu was to meet foreign ambassadors in what was described as an effort to "boost legitimacy and understanding" of a more muscular Israeli response.

At least six Palestinians have been killed since Saturday, including four by Israeli tank fire after militants destroyed an Israeli jeep with an anti-tank missile on the border with the northern Gaza Strip. Four Israeli soldiers were wounded.

The violence flared two weeks after Egypt's Islamist government mediated a cease-fire at a time when the region's being battered by the Syrian conflict, the U.S.-Iranian confrontation and political upheaval in the Persian Gulf and North Africa.

Israel is increasingly worried that jihadist factions in Gaza are working with Islamist groups in Egypt's Sinai Peninsula, which adjoins Gaza, to mount concerted attacks on the Jewish state at a time when Cairo appears to be unable to restore order in either territory.

The emergence in Egypt of an Islamist government, which seeks to amend, if not rip up, the historic 1979 peace treaty with Israel has exacerbated Israeli concerns about the country's southern border.

Concerns about the escalating surge of rocket and mortar fire from Gaza, most of it attributed to jihadist factions rather than the ruling Hamas party, that began in October, have been fueled by apparently errant shellfire hitting Israeli-held territory along the northern border with Syria.

The cease-fire line with Syria demarcated on the Golan Heights at the end of the 1973 Middle East war, in which Syria came within an ace of smashing Israeli defenses, has been Israel's quietest border since that conflict until the recent shelling.

Israel's 2008 invasion of Gaza, called Operation Cast Lead, involved up to 20,000 troops, several squadrons of fighter-bombers and helicopter gunships and even naval shelling of the coastal strip.

The operation was launched Dec. 27, 2008, following weeks of Hamas rocket bombardment of southern Israel.

The Israeli air force carried out waves of strikes with U.S.-built F-16I Sufa fighter-bombers and AH-64 Apache attack helicopters in the initial stage. The weapons involved included U.S.-made 2,000-pound, precision-guided Joint Direct Attack Munitions. The ground assault was unleashed Jan. 3.

Before the operation ended Jan. 18, 2009, the Israelis carried out some 2,400 airstrikes. Some 1,400 Palestinians, including more than 900 civilians, were killed. Israeli military casualties were 13 killed, 10 by friendly fire.

Amid global outrage, a subsequent U.N. commission headed by South African Judge Richard Goldstone reported war crimes by both sides, with particular emphasis on the Israelis.

Operation Cast Lead was launched six weeks before parliamentary elections in Israel and now the country is preparing for elections in January.

Some commentators have noted a major assault on Gaza to halt rocket attacks would likely burnish Netanyahu's right-wing credentials at the polls.

Confrontation has been welling up for months. Politically, Israel has been moving to the right for some time.

This has caused some concern, particularly Netanyahu's threat to launch pre-emptive strikes against Iran's nuclear infrastructure and his differences with U.S. President Barack Obama.

Extremist Palestinian groups, such as Islamic Jihad, have been behind most of the recent attacks on Israel but Barak has laid full responsibility on Hamas, which has ruled Gaza since a violent coup in June 2007 that drove out the more moderate Fatah faction led by Palestinian President Mahmoud Abbas.

"The firing of rockets has been relentless," he declared. "As far as Israel's concerned, Hamas is responsible for the rocket fire and all other attempts to harm our soldiers and civilians, even when other groups participate.

"It's Hamas that will pay the heavy price."