Egyptian security sources said equipment used to construct the underground border wall in Rafah came under fire on Friday, prompting an American delegation to cancel a visit to the site.

"Security reasons" were cited by the delegation for the postponement of the inspection, and Egyptian security officials could not comment on whether the shooting incident was an isolated event or part of regular attacks.

Sources in Egypt said the shots hit equipment digging 1,500 meters away from the Rafah crossing point, and noted no workers were injured and no equipment damaged.

Egypt says it is building the 25-meter deep border wall along the 10km length of the Rafah border in an effort to stop the smuggling trade that goes through the tunnels network beneath the border.

In a statement Thursday, Hamas officials said they knew the smuggling trade was harmful to Gaza society, but said they were given no choice with the continuing Israeli siege, no port, no airport or other ways to secure basic goods for Gazans.