The Egyptian army has begun to pump water from the Mediterranean Sea into underground smuggling tunnels connecting Sinai with the Gaza Strip, security officials and eye witnesses said on Friday.
The operation is aimed at ending smuggling to the Palestinian territory, security officials told dpa.
Gaza, administered by the Islamic Hamas movement, remains under a tight blockade imposed by Israel and Egypt.
The government in Cairo last year began to destroy hundreds of homes on the Egyptian side of Rafah, which straddles both Sinai and Gaza, in order to create a buffer zone.
The tunnels to Gaza are used to smuggle both goods, such as clothing and other products, as well as weapons.