"If this closure continues it will be a disaster," says Abu Taha, who runs one of hundreds of cross-border smuggling tunnels that were closed after a deadly attack in the Sinai.
For the 40-year-old businessman, the tunnels burrowed deep under Gaza's southern border with Egypt have provided him and thousands of others with a steady and lucrative source of income over the years.
But it all come to a grinding halt on Sunday night after a group of more than 30 gunmen dressed as Bedouin stormed a nearby Egyptian border police post in northern Sinai, killing 16 of them before storming the border with Israel.
The brutal attack prompted shock in Cairo, which quickly closed the Rafah border and blocked access to the smuggling tunnels, abruptly cutting off a lifeline for Gaza which has been subjected to an Israeli blockade since 2006.
"Merchandise and foodstuffs come through the tunnels, and building activities will completely stop," Abu Taha told AFP.
"Closing the tunnels will strangle Gaza and make Israel happy."
News of the closure was like a "bombshell," says Abu Mustafa, 34, who owns a tunnel specialising in building materials.
"Our business will grind to a halt. It will hurt thousands of families of both tunnel owners and workers," he says soberly.
"We are not against any Egyptian or Palestinian security measures, but we demand they reopen the tunnels, maybe with a bit more scrutiny. But if we close the tunnels, people in Gaza will die."
Palestinian security officials estimate there are hundreds of tunnels in Rafah, a sprawling city which straddles the border between southern Gaza and the Egyptian Sinai.
Omar Shaaban, an economist who heads PALThink, a Gaza-based think tank, says tunnel trade is worth an estimated half a billion dollars a year. Closing them, he says, will have a "devastating effect on all walks of life in Gaza.
"The strip got used to the tunnels as a permanent crossing point, and every sector is completely dependent on them," he tells AFP.
"Closure even for only a week will cause a serious deterioration in the situation."
Gaza has been under Israeli blockade since 2006. Although steps have been taken to ease the restrictions, Israel still maintains tight controls on what can be imported, including many basic construction materials -- which are brought in by tunnel, Shaaban says.
Closing the tunnels will mean many building projects will be stopped, which will "put 15,000 workers in the building sector out of work."
"And don't forget that fuel comes in every day, and delaying this will worsen the electricity crisis and will stop work at bakeries, in factories and in transportation."
Until very recently, Gaza had been living through its worst power crisis in living memory, but the situation had eased considerably with the delivery of millions of gallons of Qatari fuel through Egypt and Israel.
But Sunday night's attack has put everything on hold.
Long lines of cars could be seen outside petrol stations across the coastal enclave on Monday as panic buying kicked in, with many outlets running dry.
"The Egyptians are blocking trucks carrying goods and fuel from reaching the tunnels," says Abu Jihad, who runs a fuel tunnel.
Although he agreed that Egypt needed to act to catch the perpetrators, Abu Jihad said closing the tunnels would hit Gaza very hard.
"Who will provide food and drink for the people here? How will the power plant function without fuel? Life here depends on tunnels."
Within hours of the raid, which saw 35 gunmen storm the Egyptian post then crash two vehicles over the border near Israel's Kerem Shalom crossing, Hamas police went on high alert, reinforcing its numbers along the frontier to keep people away.
Ihab al-Ghussein, spokesman for the Hamas-run interior ministry, says the state of alert will continue "for as long as necessary" to ensure no perpetrators try to flee into Gaza.
The attackers, he says, were not from Gaza.
"Gaza had nothing to do with the attack and no one from Gaza sneaked out through the tunnels," he insists, rejecting "baseless accusations" implicating Palestinians, which he describes as "the Israeli narrative."
Deputy foreign minister Ghazi Hamad told AFP the Rafah crossing could be reopened "in the next few days if it is proven that no one in Gaza was involved in the attack, but I think tunnels will take some time.
"We closed the tunnels to prevent anyone from sneaking in or out of Gaza during the pursuit of the offenders and those who backed them."
Closing the tunnels, he admits, "affects the strip negatively as everybody knows Gaza depends on tunnels to get food, construction materials like cement, and fuel."