TYRE, Lebanon — The warning on the leaflets that fell like confetti over Tyre yesterday was plain: Any vehicle seen moving in the city would be regarded by the Israeli air force as hostile.

Not that many people had been driving in Lebanon’s southernmost city. Emptied of nearly its entire population after three weeks of heavy bombardment, its potholed roads present a challenge for the bravest of drivers.

Ambulances and even mopeds, picked out by remote-control Israeli drones, have been hit by missile fire.

As the front line drew ever closer, a few vehicles were on the move in the tiny Christian quarter, the only area so far untouched by Israeli fire.

But silence reigned elsewhere, punctuated only by Israeli shells and occasional, outgoing Hezbollah rockets.

Most aid agencies have had to suspend delivery of emergency relief. The last bridge connecting Tyre to the outside world was bombed on Monday.

Israel has told the United Nations it can no longer guarantee the security of its convoys in a buffer zone that it is trying to create south of the Litani River.

“We can’t drive anywhere outside the Christian quarter,” a Red Cross worker said as he unloaded food from an ambulance. “It is too dangerous.

A man told us his wife and four children are trapped in the rubble of his home, which was bombed last night, but we can’t go there because we have not received permission from the Israelis.”

Ninety percent of people have fled the Christian quarter, and the rest of the city feels like a wasteland.

But in small pockets of the northern suburbs, a few still eke a precarious existence. Refugees from southern villages cower in apartment blocks with the few Tyre residents unable or unwilling to leave.

The two communities, forced by war to become neighbors, regard each other with unease. The refugees come from Hezbollah’s strongholds and see the residents of Tyre, where the movement is less popular, as potential Israeli spies.

Tales are told of Lebanese agents daubing the homes of Hezbollah fighters with invisible paint that can be picked out only by Israeli jets.

Najat Karouni, 30, and her aunt are the only residents left in her neighborhood, save for two refugee families sheltering on the first floor of her block of flats.

The refugees seem convinced that Ms. Karouni must be a spy.

“Everywhere I go, they follow me, whether it is to the shops or even to the tap downstairs when I wash my hands,” she said.

Perhaps they cannot understand why she did not flee. But for Ms. Karouni, the decision was a simple one.

“I love the city,” she said. “I was born here, and if I have to die, I want to die here.”

Everyday life has become terrifying. Standing on her balcony — rebuilt after an Israeli bomb destroyed part of the flats during the 1982 invasion — she pointed to a coffee stain on her jeans.

“I was sitting here last night when a bomb fell just down the road, and I spilled my coffee in the shock waves,” she said. She laughed as she added: “All my jeans are like that. It happens every day.”

As if on cue, three bombs fell in succession on a nearby suburb and filled the air with smoke.

Walking through her neighborhood, she pointed out the crater in the floor of the next-door block of flats that was hit on Monday night.

Around the corner, another block had been flattened. Under the rubble lay her cousin, Hussein Karouni, killed two weeks ago.

“We still can’t get him out,” she said.