WASHINGTON - Rockets launched yesterday into northern Israel from a Palestinian refugee camp in Lebanon heightened fears that the border region is on the verge of a broader new conflict between Israel and Islamic militants.
Mideast diplomats rushed to point out that the rockets were launched not by Hezbollah, the Lebanon-based radical militia that fought Israel to a bloody standstill in 2006, but by independent Palestinians.
Others saw a chilling reminder that events in the volatile region can easily spin out of control and that serious fighting could erupt on Israel's northern border as the violence in Gaza intensifies.
"If there are more attacks, if an Israeli is killed by one of these rockets, then the pressure will increase" for a major Israeli retaliation, said David Hartwell, Mideast analyst in London for Janes Information Group. That is just the kind of unintended escalation that ignited the war in 2006.
Hezbollah denied it was involved in the attack, which struck a nursing home in Nahariyah, slightly injured two Israelis and left others in shock, Israeli news services reported. Yesterday, Israel fired a few desultory artillery rounds into southern Lebanon.
"There are rules of the game; each side knows how far they can push it," said Hartwell. "But it does happen that one side or the other steps outside the rules, and the miscalculation happens and there is a major spillover of violence across the border."
With the northern border area newly tense, Israeli air and ground forces continued to bloody the leadership of Hamas, the militant government of Gaza. As the humanitarian crisis there worsened, Israeli forces were moving into position to launch what could be a savage battle to eliminate Hamas as a functioning organization.
Analysts watching the region said they are worried that if Hamas appears to be on the verge of disintegration, Hezbollah or others might begin launching more rockets from bases in Syria and Lebanon into northern Israel, as a diversion to help save their fellow radical Islamist group in Gaza.
"If Hamas is on the verge of strategic defeat, I believe Hezbollah or radical Palestinian groups in Lebanon are going to shell northern Israel," said Kenneth Brower, a senior defense consultant in the U.S. and Israel.
Behind these calculations lurks Iran, which trains, arms and - U.S. intelligence officials believe - controls both Hamas and Hezbollah.
The role Tehran chooses to play - to inflame the violence or to help douse it - will determine whether the conflict in Gaza explodes into a wider war.
In Gaza so far, despite Palestinian casualties that have climbed to about 750 dead and thousands wounded, Israeli strike jets, tanks, infantry artillery and combat engineers have not yet made heavy armored thrusts into population centers in Gaza city, Khan Yunis and the Rafah refugee camp, according to Israeli officials.
"As soon as it [a determined Israeli ground offensive] starts, Iran faces a strategic dilemma: let Hamas go under or activate a second front," Brower said. "My guess is: a second front."
A wider war is possible if Iran instigates it, agreed Bruce Hoffman, a terrorism expert at Georgetown University's Edmund A. Walsh School of Foreign Service.
"Iran calls the shots, and Hezbollah will not do anything unless Iran prods or encourages them to," Hoffman said.
Nevertheless, there are ominous signs of potential trouble ahead.
Iran has used its nuclear development program, its sponsorship of Hamas, Hezbollah and armed insurgents in Iraq and - until recently - its record oil profits, to chart a course toward becoming the region's superpower.
Since the 2006 war, it has trained more than 4,000 Hezbollah fighters in Iran in rocket operations and other advanced military operations, according to Mideast officials. Israeli officials believe Hezbollah has more than 42,000 missiles that can range the length of Israel from hidden bases, mostly in Syria.
On its side, Israel ordered the mobilization of "tens of thousands" of additional army reservists this week even as its troops were pouring into Gaza. The number of call-ups was far beyond the numbers needed in Gaza, analysts noted.
The logic of a "second front" in what Israel has defined as a war against terrorists might seem contorted, given Israel's overwhelming advantage in conventional military power.
Hezbollah's leaders "are not just some suicidal lunatics anxious for the quickest martyrdom available," said Stephen Biddle of the Council on Foreign Relations.
He said there are "substantial disincentives" for Hezbollah to get involved, including the near-certainty of heavy retaliation by Israel.
But fine political calculations might be difficult to maintain amid the growing bloodshed in Gaza and as the political atmosphere heats up, with both Iran and Israel nearing critical elections.
Israeli Defense Minister Ehud Barak and Foreign Minister Tzipi Livni are jockeying to become the new prime minister in next month's voting, perhaps adding pressure to act decisively if rocket attacks cause serious casualties in northern Israel.
Iran, with presidential elections scheduled for June, has been battered economically by falling oil prices and politically by the declining violence in Iraq and the negotiated draw-down of U.S. troops there.
In advance of the voting, Iran's President Mahmoud Ahmadinejad might be seeking to reassert Iran's regional prowess, according to some analysts. Saving Hamas, in the eyes of Tehran's leaders, could pay off handsomely.
"It's true that Iran would seek to take action to avert the destruction of Hamas in Gaza," said James Phillips, a senior Mideast researcher at the Heritage Foundation, a Washington think tank.
For Israel, the prospect of new rocket attacks from the north is deeply worrying, according to Juan Cole, Mideast expert at the University of Michigan.
Although largely unsophisticated with poor guidance, the rockets fired by Hamas and the Lebanon-based Palestinians are nerve-wracking for Israelis, officials acknowledged this week.
During previous cycles of rocket and terrorist attacks in Israel, the flow of immigrants into Israel slowed and the rate of people leaving accelerated, Cole said. About half of the Americans who migrated to Israel have returned to the United States, he said, and Israel has lost nearly 10 percent of its 1 million immigrants originally from Russia.
Israel's demographic vulnerability in the uncertain security situation, Cole wrote this week, "is Israel's Achilles heel."
That might give Hezbollah and Iran even more reason to weigh an attack.
According to Iran's FARS news agency, senior Iranian officials shuttled this week between Damascus and Beirut, meeting to discuss the situation in Gaza with Syrian and Lebanese officials as well as representatives of Palestinian organizations.
In what sounded like a warning against Iranian meddling, Livni, the Israeli foreign minister, told reporters Monday that "when Israel is targeted, Israel is going to retaliate."
She went on to divide the region sharply into friends and foes, or as she put it, "moderates and extremists." She said Hamas had chosen the extremist side.
Hamas "works with Iran, gets weapons from Iran, its headquarters are in Damascus, and it works closely with Hezbollah," she said, adding that its choice justifies Israel's "fight against extremism and terror."
There is a wild card in these calculations as well: Hamas-affiliated fighters based in refugee camps in southern Lebanon who are believed to have obtained rockets from Iran.
Such groups might act independently regardless of instructions from Tehran.
"Hamas has considerable support in those camps," said Phillips. "One of my great concerns is that they will launch rockets hoping to draw Israel into a war with Hezbollah."