Egyptian forces have flooded smuggling tunnels under the border with the Palestinian-ruled Gaza Strip in a campaign to shut them down, Egyptian and Palestinian officials said.

The network of tunnels is a vital lifeline for Gaza, bringing in an estimated 30 percent of all goods that reach the enclave and circumventing a blockade imposed by Israel for more than seven years.

Reuters reporters saw one tunnel being used to bring in cement and gravel suddenly fill with water on Sunday, sending workers rushing for safety. Locals said two other tunnels were likewise flooded, with Egyptians deliberately pumping in water.

"The Egyptians have opened the water to drown the tunnels," said Abu Ghassan, who supervises the work of 30 men at one tunnel some 200 meters (yards) from the border fence.

An Egyptian security official in the Sinai told Reuters the campaign started five days ago.

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