By Martin Asser
BBC News, Tyre
A missile strikes close to a road jammed with fleeing people
Israel has ordered the civilians of southern Lebanon to leave their homes and thousands of families are heeding that advice - at least they are trying to.
But the Israeli military onslaught around the southern city of Tyre is so fierce, the trip is too daunting for many inhabitants.
Bridges on the main road north to Sidon have been rocketed by the Israeli air force, forcing traffic to make detours up into the hills.
Laser-guided 450kg (1,000lb) bombs have also dug huge craters across half the highway, funnelling the chaotic melee of taxis and private cars into one painfully slow lane.
And this gives no chance for south-bound drivers heading towards Tyre, many of whom say they are on humanitarian missions for people trapped in their homes by the bombing.
Tempers are frayed as people wait for hours under the scorching sun, each one desperate to reach a friend or relative in need of rescue.
Near one of these choke points, at a sand and gravel dyke, 8km (5miles) north-west of Tyre, dozens of cars were waiting to cross the Litani river - a natural obstacle between Tyre and Sidon in addition to the Israeli-made ones now also on the way.
The journey out of southern Lebanon is slow and fraught
As the traffic churned through the dust and sludge, the rumble of two Israeli warplanes overhead turned into a terrific snarl, as they swooped down to fire their missiles at an unseen target in the next valley.
Moments later, thick grey smoke rose over the horizon and a new sense of urgency gripped the cars packed with men, women and children crossing the river to escape.
"You are British?" one driver leaned over to ask me, as I continued to photograph his wife and seven children in his beat-up Mercedes.
"Tell Tony Blair to stop this!" he said with feeling and his veiled teenage daughters, the eldest holding the large family Koran open in her lap, nodded in agreement.
As the plume of smoke cleared, the cars queuing up pressed on towards the north, and the next nerve-jangling choke point a few kilometres up the road.
Parents are trying to take their children to safety
How quickly the traffic in southern Lebanon under Israeli bombardment has come to resemble that in the West Bank (and Gaza, until last year) under Israeli occupation.
The difference is that these disrupted journeys are being made to escape a terrifying air bombardment.
Israel says it is doing everything to avoid civilian casualties, but will continue and indeed escalate its attacks unless the Hezbollah militant group frees two soldiers it captured inside Israel 11 days ago and stops its rocket attacks.
With little chance of that in present circumstances, thousands of people have been jamming the highways and mountain roads heading north.
But after Saturday's early afternoon missile strike so close to their escape route, the flow of internally-displaced Lebanese dried up almost completely.
"I want to get my children out of here," said a man who had fled from Qana and is now sheltering at an emergency gathering point in Tyre.
"But they are too scared of the bombing and I can only take them out when it is quiet."