Egypt has started demolishing homes along its border with the Gaza Strip to create a buffer zone.
The government says the measure is intended to prevent an influx of weapons and fighters, and is "vital for national security and stability".
The operation was rushed forward following a wave of deadly attacks in Egypt's Sinai Peninsula, a strategic but increasingly lawless region bordering Gaza, Israel and the Suez Canal.
A three-month state of emergency was declared after the latest attack - a suicide bombing on Friday that killed at least 30 soldiers.
Egyptian President Abdel Fattah el-Sisi warned the attack was carried out with "external support".
Appealing to the nation, he said: "I'm addressing all Egyptians, be vigilant. A plot is being woven against all of us.
"We and all Egyptians must join forces to address this challenge… It is a huge war, Egypt is facing a huge war."
Homes are being flattened using bulldozers and dynamite to create the 500-metre deep buffer zone. Thousands of people have been ordered to leave the area.
So can Egypt justify its action as a necessary security measure? Or does it constitute a breach of human rights?
Presenter: Mike Hanna
Eid al Marzouqi - political activist opposed to the marginalisation of people in Sinai.
Yehia Ghanem - an Egyptian journalist and Fellow from City University in New York.
Hassan Nafaa - a political scientist at the University of Cairo.
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Source: Al Jazeera