Palestinian militants stormed an Israeli border crossing today and killed two civilians, sparking fears of another escalation in violence between the sides.

Israeli ambulance crews said the victims, believed to be in their 30s, were killed after militants stormed the Nahal Oz crossing under cover of mortar fire the northern Gaza Strip.

Once on the Israeli side of the border, the gunmen engaged in a gun battle with the Israeli Army. The military says one of the militants was killed, another captured and two fled back into Gaza.

Islamic Jihad, a sister group of Hamas, the Islamist group which runs Gaza, claimed responsibility for the attack along with the Popular Resistance Committees, a cross-party coalition of militia.

Israel has not confirmed what retaliation it would take for the raid, but the Army regularly launches often-bloody bombing raids against suspected militant targets in Gaza. Mark Regev, a government spokesman, said this afternoon that Hamas “will be held accountable" for the operation.

The raid comes after Hamas-affiliated militants threatened to storm Gaza's borders with both Israel and Egypt in protest against a continuing international blockade imposed on the territory since the Islamists seized control of it last summer.

Earlier today, another gun-battle near another northern border fence between Gaza and Israel killed Saif Bissan, 21, an Israeli soldier, and lightly wounded two others, the military said. A Palestinian militant was also killed.

As the events unfolded, the Egyptian government issued Hamas with a stern warning that it would not tolerate any attempt by militant to repeat the blowing up of the Rafah border crossing, separating Gaza and Egypt.

In a statement, published by the Egyptian Mena news agency, it said it would "not take lightly the protection of its frontiers against any attempt to violate them, no matter who they are."

It added: "Egypt’s borders are a red line you cannot cross. Egypt is capable of responding to any attempt to violate its frontiers."

So far 375 people, mostly Palestinian militants, have been killed since the US-hosted peace summit in Annapolis in November agreed to restart talks between Hamas's main rival, Fatah, and Israel.

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