Gaza's Hamas rulers have closed hundreds of tunnels running under the territory's border with Egypt due to health concerns over some smuggled items, an official said on Wednesday.
"Less than 270 tunnels are operating now, down from around 1,200 tunnels in 2010," the official told AFP on condition of anonymity.
"Many of them were closed down because they were used to smuggle banned materials that harm citizens."
The Hamas government forbids the importation of drugs and any other items it considers potentially harmful into the Palestinian enclave which is under an Israeli blockade.
Another Gaza source said Hamas had closed about 900 tunnels, and a tunnel operator said others were being flooded from the Egyptian side.
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"The Egyptian security forces pump water into the tunnels which leads to their collapse and closure," said Abu Samir, owner of a tunnel near the Gaza border town of Rafah.
"There is no work in Gaza," he told AFP.
"What can we do to live? The tunnels are the most important source of livelihood in Gaza now... no matter how many times they demolish them we will rebuild."
Abu al-Assad, another tunnel owner, said: "The Egyptians closed down the tunnels twice after the (outbreak of their) revolution but I rebuilt after months because to us it is a matter of life and death."
Hamas, he added, had allowed tunnels to multiply and issued permits for their use to bring in essential commodities, after the Islamist movement seized control of the coastal strip in 2007.
The tunnels have been a vital lifeline for the flow of food, clothes, building materials and fuel into the impoverished territory, which Israel has blockaded since 2006.