Israel fears more weapons will be smuggled into Gaza after the easing of restrictions by Egypt at the Rafah border crossing.
Many Palestinians are now being allowed to cross freely for the first time in four years after the crossing opened last night.
Egypt, along with Israel, has been blockading the border since Hamas took control of Gaza.
The crossing will now be open from 9am - 9pm every day except Fridays and holidays.
Men aged between 18 - 40 still require a permit, and trade is prohibited with Egypt saying it will search everyone crossing.
Although the border will still be closed for trade, the opening of the Rafah crossing is expected to provide a major economic boost to Gaza.
Israel's foreign ministry hopes Egypt can stay on top of the situation.
The border has been effectively closed since Israel imposed a blockade on Gaza in June 2006.
The United Nations has called the blockade illegal and repeatedly demanded that it be lifted.