Israeli tanks and troops moved into Gaza Saturday to begin a ground offensive against Hamas militants.

There are reports of heavy gun battles and artillery was heard east of Gaza City where Hamas fighters are deployed.

Defense officials said about 10-thousand soldiers had massed along the border before the troops began to move in.

It is not immediately clear how far into Gaza the Israeli forces will penetrate, but Israeli officials insist it will be a "lengthy operation."

Hamas leaders claimed they prepared a violent welcome for the Israelis and threatened to resume suicide attacks inside Israel.

The Israelis began the offensive one week ago to halt militant rocket fire aimed at southern Israel.

The first week of fighting claimed more than 450 Palestinian lives while four Israelis were killed by rocket fire.