As the bombs rocked Gaza City, the telephone in the apartment where Mohammed was holed up with eight members of his family rang. When he picked it up, he heard a recorded voice similar to the automated sales pitches used by telemarketing companies.

“It said that if I was hiding weapons or terrorists, my house would be bombed,” Mohammed, 26, a teaching assistant, said. The software engineer, who gained his master’s degree at the University of York, had been trying to leave home for six months to study for a PhD in Turkey, but Israel had denied him permission to leave. Now it was telling him to flee, but there was nowhere to go.

Such phone calls have become common across the Gaza Strip, in what many see as a new stage in the psychological campaign to destabilise the Hamas-controlled territory.

The messages vary, spreading fear and confusion, according to Sari Bashi, of the Israeli human rights organisation Gisha. Some tell people that they must leave their homes immediately to avoid being harmed; others are similar to the warning received by Mohammed. Some are direct threats: “Leave your house; it will be bombed soon.” The calls are causing such panic that the Palestinian phone company has issued its own recorded messages telling people to ignore the Israeli threats.

“This is psychological warfare,” Linda al-Ghais, 32, a microbiologist and mother of three living in Gaza City, said. “We don’t know if it’s true or not, if they’ll bomb us or not. Everyone is very frightened.”

Mohammed thought that the calls may be an attempt by Israel to cover itself in the event of civilian homes being hit. “They are doing this to show they are taking care in case civilians are hit, but clearly they are not taking care. Hundreds of people have died, many of them civilians and even children,” he said.

An Israeli military spokesman declined to comment on the calls.

Ms Bashi said that the tactic was a clear case of psychological warfare being waged against civilians. “Gaza isn’t comparable to the wars in Leba-non or even in Sderot [the Israeli town that has borne the brunt of Palestinian rocket fire from Gaza]. In Gaza, the bombing is widespread throughout a narrow, densely populated strip of land whose borders are sealed. You’ve nowhere to go,” she said.

The Israeli telephone messages give no indication of where people may find shelter. “If the message is that people are being given a chance to leave their homes, well, there’s nowhere to go,” Ms Bashi said.

Many people who receive the messages are too scared to tell neighbours of the warning for fear that they will be branded as Israeli collaborators who have received a tip-off. That can cost you your life in Gaza.

One family received a telephone message that their house was about to be bombed and fled without informing their neighbours, Ms Bashi said. When the house was attacked, the neighbours were furious that they had not been warned by the family.

Israel is not alone in carrying out what the military calls “psy-ops”:

Hamas has said that the Israeli bombardment has wounded the Israeli soldier whom it has been holding prisoner at an undisclosed location since a cross-border raid in the summer of 2006.

Hamas officials told Israeli and Egyptian media that Corporal Gilad Schalit had been hurt, but did not elaborate on his injuries.

The Israeli army prides itself on its policy of never leaving a man behind, alive or dead, and in the past has released hundreds of prisoners to secure the remains of fallen soldiers.

“We were expecting there’d be all sorts of rumours and reports about Gilad,” an Israeli army official said. “We approached the family beforehand and warned them what to expect.” The army is suspicious of the reports, believing that the soldier is too important an asset for Hamas to allow any harm to come to him. It could not, however, discount the reports. “Anything is possible,” the army official said.

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