Three Mideast combatants who once traded lethal blows against each other have now formed a stunningly unlikely alliance against what they consider as a far deadlier menace in their region: the Islamic State (ISIS) terrorist group.

Israel, Egypt, and the Palestinian militant group Hamas have tacitly agreed to close ranks to stop the ISIS from creeping into their territories, the Washington Post reports.

The move was prompted by the increasingly sophisticated and daring attacks by ISIS forces in the region.

Last week, Hamas deployed several hundred fighters to Gaza's border with Egypt's Sinai peninsula as part of a deal with Cairo to keep ISIS militants from entering Gaza.

Earlier, Israeli Prime Minister Benjamin Netanyahu lauded his country's decision to erect a new fence along the Israel-Egypt border, saying that without the new barrier "we would have been overflowed by thousands of ISIS fighters from Sinai."

The threats posed by ISIS have led to the biggest cooperation between Egypt and Israel since their 1979 peace deal, according to officials from both countries.

The Egyptian and Israeli forces, with support from Hamas, are up against a jihadist group that has grown bolder since it claimed responsibility for the bombing of a Russian charter flight over the Sinai Peninsula in October, killing all 224 people aboard.

The well-armed ISIS affiliate group known as Wilayat Sinai has been attacking Egyptian soldiers, overrunning military posts and targeting them with roadside bombs.

Egyptian intelligence sources say the group poses a serious challenge. "They have genius strategists," said Mohannad Sabry, an Egyptian journalist and author of a book on the Islamist insurgency in the Sinai.

In a recent tweet, the ISIS claimed responsibility for destroying an American-made Egyptian M60 tank near Gora airport, used by United Nations peacekeepers as a base.

On Friday, the ISIS militants claimed that they have cut off an Egyptian military supply route to the airport after they attacked a convoy carrying food and arms.

Fierce fighting between the militants and the Egyptian army has reportedly been occurring regularly in the Sinai.

The ISIS has hundreds of fighters based in the Sinai, analysts and military officials say. These militants do not hold major territory or stage large-scale offensives, preferring to work within small cells to carry out hit-and-run attacks, the officials say. Their weapons include antitank ground missiles and rocket-propelled grenades, many of which were smuggled in from neighbouring Libya in the aftermath of the 2011 revolution that toppled dictator Moammar Gaddafi.