Taken by the Middle East correspondent for a Danish newspaper, the picture shows rows of people sitting on plastic chairs looking out over the Gaza Strip as rockets and explosions light up the night sky.

Allan Sørensen, who posted the image, wrote that it showed a kind of “cinema” on the hilltop outside the Israeli town of Sderot, and a caption added: “Clapping when blasts are heard.”

Sørensen’s newspaper, the Kristeligt Dagblad, reported that the gathering involved more than 50 people who had transformed the hill into something “most closely resembling the front row of a reality war theatre”.

It said that people were seen taking popcorn up onto the hill with their chairs, and that they sat cheerfully smoking hookahs.

“We are here to see Israel destroy Hamas,” said Eli Chone, a 22-year-old American who lives in Israel.

Sørensen’s tweet was met with anger by fellow Twitter users. One user wrote: “If this is true then God help us all. What’s become of the human race?”

Another said: “This is the most gruesome image I’ve seen the last few days.”

Israeli residents, mostly from the southern Israeli city of Sderot, sit on a hill overlooking the Gaza Strip, on July 12, 2014, to watch the fighting between the Israelis and Palestinians militants

Further images have since emerged showing larger crowds on subsequent days – suggesting that the so-called “Sderot cinema” was far from a one-off. They showed groups standing and pointing out to the horizon, and one had even brought a sofa up onto the hilltop.

Meanwhile, Israel today launched its first ground offensive in a bid to destroy a rocket-launching site in northern Gaza.

Troops were sent in early on Sunday, in a brief raid which left four soldiers slightly wounded after an exchange of gunfire, the military said.