Lethal strikes in Gaza and a deadly suitcase bomb in Jerusalem on Wednesday confirmed fears that violence between Israelis and Palestinians is on the rise again after nearly two years of relative calm.
Virtually ignored for the past three months as the neighbouring Arab world plunged into turmoil, the 62-year-old Middle East conflict has slid quickly back into its familiar cycle of bloody attack, retaliation and counter-attack.
Nine Palestinians and one Israeli have died since Tuesday.
There is no obvious connection between the suddenly surge of violence and revolutions in Tunisia, Egypt, Yemen and Bahrain, or the civil war and Western military intervention in Libya.
Western diplomats on Wednesday said they were unable to point with confidence to any particular triggering factor.
But senior Israeli and Palestinian officials and Western diplomats have all warned in recent months that without a viable peace process and the hope of a Palestinian state, violence would almost certainly fill the vacuum.
Peace talks have been suspended since September 2010.
LONG-RANGE
Palestinian rockets fired from Gaza struck two cities deep in Israel on Wednesday, wounding a resident and prompting Prime Minister Benjamin Netanyahu to threaten lengthy "exchanges of blows" with the Hamas-ruled Gaza Strip.
The attacks on Beersheba and Ashdod followed a surge of shelling between Israel and Hamas Islamist fighters in the enclave, in which Israeli fire killed four Palestinian civilians and five Palestinian gunmen.
On Wednesday afternoon a bomb exploded near a bus stop in a Jewish district of central Jerusalem, killing one woman and injuring at least 30 people.
Police said it was a clearly a Palestinian terrorist attack. It was the first in Jerusalem in seven years.
At the height of a Palestinian uprising that began in 2000 and continued for five years, Palestinian militants carried out dozens of often deadly bombings in Jerusalem.
There was no immediate claim of responsibility linking the attack to the deaths in Gaza, where Hamas declared a state of emergency that included evacuating all security compounds in case of Israeli air attacks.
In the West Bank, Palestinian Prime Minister Salam Fayyad condemned the Jerusalem "terrorist operation", saying such acts damaged the Palestinian cause and contradicted "our people's legitimate endeavour to gain its freedom by peaceful means".
TIME FOR BLOWS
Netanyahu expressed regret for the Israeli fire that killed four Gaza civilians on Tuesday, and said Israel sought no escalation. But some members of his cabinet said there may need to be a wider offensive on Gaza to curb its militants.
Israel's three-week war on Gaza in early 2009 killed around 1,400 Palestinians, drawing heavy international censure.
Rocket and mortar fire from the defiant Islamists never totally ceased afterwards but occurred at a greatly reduced rate until last weekend, when dozens of explosions peppered southern Israel, and Israeli aircraft and artillery struck back.
"No country would be prepared to absorb protracted missile fire on its cities and civilians," Netanyahu told parliament.
"It could be that this matter will entail exchanges of blows, and it may take a certain period of time, but we are very determined to strike at the terrorist elements and deny them the means of attacking our citizens."
Israelis in the past two months have remarked on the novelty of the Middle East conflict being out of the spotlight, as revolt against Arab autocrats preoccupies the world.
But the stabbing to death of an Israeli settler family in the West Bank early in March was a reminder that violence lurks just beneath the surface of their fragile "interim" accord with the Palestinians, in effect since 1993.
INTERNAL SPLIT
Some analysts suspect the burst of Gaza rocket fire at the weekend was meant to wreck a bid by Palestinian President Mahmoud Abbas to mend the split between Hamas and his Fatah movement, which wants peace with Israel and has renounced the "armed resistance" to which the Islamists remain committed.
Abbas may have called the bluff of Hamas this month when he accepted its offer to hold face-to-face reconciliation talks in the Gaza Strip, following a rally by about 100,000 Palestinians saying they were tired of the split and wanted unity.
The swift rise in tensions over the few days has made a visit by Abbas to Israel-blockaded Gaza impossible, and may have thrust the issue of reconciliation into the background.
On the other hand, say analysts, it could be the Islamist way of proving that Hamas, not Fatah, is the only true defender of the Palestinian people, ready to face up to Israel, and should be entrusted with leadership of the national movement.
The Islamists are wary of the wave of popular protest sweeping Arab countries, trying to co-opt and control any local manifestations of the general demand for a change of policy, but also cracking down on attacks on their leadership of Gaza.
Gaza political analyst Talal Okal believes Hamas's escalation of violence was a calculated move.
"When in the midst of complete calm, Hamas comes and announces it has fired over 40 mortar bombs it becomes clear that Hamas is attempting to cover up for the crisis that resulted from the youth movement in the streets and the initiative by (Abbas) and his potential visit to Gaza."
Israeli Vice Premier Silvan Shalom on Wednesday said Hamas may have opened a new front with Israel "to stop any possibility of dialogue among the Palestinians, or to come to the intra-Palestinian negotiation in a far stronger position".
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