Egyptian police have seized a flock of 560 sheep set to be smuggled into the Gaza Strip through underground tunnels, a security official said Monday.

The flock was discovered on Sunday night, along with the entrances to six tunnels in the Salah el-Din district north of the Rafah border crossing, the official said.

Four out of the six tunnels were comparatively large at three meters in diameter, the official added.

Police also seized five tons of cement and found a half ton cache of TNT hidden in near the border.

Gaza has been under a crippling Israeli and Egyptian blockade since Hamas violently seized control of the coastal territory in June 2007.

The tunnels are the main artery for food entering Gaza, but they are also a conduit for weapons to Gaza militants.

Israel destroyed many tunnels during its recent three-week military offensive in Gaza, but smuggling continues.