The Lebanese Shia group Hezbollah has captured two Israeli soldiers in a cross-border raid.
By Roger Hardy
Middle East analyst, BBC News
Israel is likely to increase pressure on Lebanon and Syria
The abduction marks a new escalation of the crisis which began two weeks ago when a young Israeli soldier was captured by Palestinian militants.
Even by the standards of the Middle East, the twists and turns of the latest regional crisis have been extraordinary.
The capture of a young Israeli soldier, Corporal Gilad Shalit, on 25 June quickly led to a war of wills between Israel and the Palestinians.
Israel's Prime Minister, Ehud Olmert, piled on the pressure on a Palestinian population already under economic siege following their election of a Hamas-led government in January.
He has pummelled Gaza, rounded up Hamas officials - including government ministers, and threatened dire consequences if the young soldier is harmed.
A series of Israeli attacks and incursions has left some 50 Palestinians dead.
But to Mr Olmert's evident frustration, neither psychological pressure nor military action has produced the desired effect.
Corporal Shalit is still in captivity. Mediation efforts by the Egyptians and others have not borne fruit.
The Palestinians still launch home-made rockets into Israeli territory.
Now a new actor has made a dramatic entrance onto centre-stage.
By capturing two Israeli soldiers in a cross-border raid, Hezbollah has raised the stakes.
The raid is both a gesture of solidarity with the Palestinians and a way of adding to the pressures on Ehud Olmert.
The Israeli prime minister lacks the toughness and the military background of his predecessor, Ariel Sharon.
His handling of this evolving crisis will test his leadership - and determine the outcome of his ambitious plan to withdraw from large parts of the West Bank by 2010.
Hezbollah has increasingly come to play the role of big brother to Hamas.
Even though the Palestinian group is Sunni and the Lebanese group Shia, Hamas regards Hezbollah as a role model.
Israel's decision to withdraw its forces from southern Lebanon in 2000 was, at least in part, the result of Hezbollah's military operations.
Hamas regards Hezbollah as a role model
The group's regional standing rose significantly.
Some Palestinians deduced - wrongly, in the view of many experts - that the only way to liberate Israeli-held territory was by force.
Moreover Hezbollah has pioneered the practice of capturing Israeli soldiers or civilians and driving a hard bargain over their eventual return.
Two years ago it exchanged an Israeli businessman and the remains of three Israeli soldiers for some 400 Palestinians and Lebanese held by the Israelis.
Complicating this latest flare-up in regional tension is the fact that Hezbollah has the backing of both Syria and Iran.
Israeli and American officials have already been saying Syria is partly to blame for the capture of Corporal Shalit since it plays host to part of the Hamas leadership.
The pressure on both Syria and the Lebanese government will now intensify.