Israel's military distributed a video yesterday which it says shows a tunnel that Hamas militants planned to use to launch attacks.

A military spokesman said 10 tunnels were discovered during the first day of Israel's ground invasion into the Gaza Strip. A commander at the site described the tunnel access point and said it was aimed toward Israel.

"As you can see, we've already targeted this area, this is what's left. This is the access point that tunnels through to Israel. It starts with a descent, which proves it is a tunnel. After digging we revealed a small and narrow access point which can fit one or two people at a time," said the commander, who was not identified.

"That area is their shelter, in case of IAF (Israeli Air Force) strikes there's even a bathroom and shower. Over there is a resting area they built themselves," he added, pointing to a makeshift shelter on a nearby mound.

The discovery came as Israel warned it could "significantly widen" a Gaza land offensive yesterday but was cautioned by its main ally, the United States, about the risks of further escalation as Palestinian civilian deaths mounted.

Palestinian officials said 58 Palestinians, at least 15 of them under the age of 18, have been killed since Israel sent ground forces on Thursday into the densely-populated enclave of 1.8 million Palestinians.

The Israeli military said it killed 17 Palestinian gunmen while another 13 surrendered and were taken for questioning after the infantry and tank assault began in the Islamist Hamas-dominated territory.

One Israeli soldier was killed in an apparent friendly fire incident, the military said, and several other troops were wounded in the ground operations. It said some 150 targets, including 21 concealed rocket launchers and four tunnels, have been attacked.

Israel says its forces have focused so far on seeking out tunnels Palestinian militants might use for cross-border raids and moving weaponry.

One such infiltration was narrowly thwarted on Thursday, with the army saying it had repelled 13 Hamas gunmen after they emerged from a tunnel close to an Israeli farming community.

In all, 291 Palestinians - most of them civilians - have been killed since fighting began on July 8, Gaza officials said. At least 50 were under the age of 18.

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