Israel shut its border crossings with Egypt on Wednesday after a car bomb exploded in the North Sinai capital of El-Arish. The attack was part of a series of coordinated Islamic militant assaults on checkpoints within the Egyptian province. At least 50 people—many of them Egyptian soldiers and policemen—are believed to have been killed. Four Israelis were reportedly injured, as well. A group called Sinai Province, an affiliate of the Islamic State, have allegedly used Twitter to claim their responsibility for the attacks, reported Haaretz, including attacks to at least 15 security sites, and three suicide attacks.

The incident follows the Islamic State’s release of a video message released on Tuesday called, “A Message to Our People in Jerusalem,” reported The Jerusalem Post. In it, a masked ISIS member proclaims:

“‘We will uproot the state of the Jews (Israel) and you and Fatah, and all of the secularists are nothing and you will be over-run by our creeping multitudes.'” He addresses the message to the “tyrants of Hamas.”

The Jerusalem Post reported Israel’s major concern behind the solidified border is that the Egyptian government is unable to contain the recent surge of Islamic militant insurgency, particularly in light of a car bomb that killed the Egyptian prosecutor-general in Cairo on Monday. The Israel-Sinai border crossings at Niztana and Kerem Shalom have now been closed, and the IDF is closely monitoring the entire border area with Egypt as well as with Gaza, because of the attacks. In 2013, Israel fenced off its border with the Sinai Peninsula with a five meter-high razor-wire barrier, complete with security cameras, primarily to prevent African migrants from illegally slipping across the Egyptian border.

The closing of the Sinai border crossing follows the news this week that Israel plans to erect a new security fence along its border with Jordan. On Monday, the Israeli government announced that the appropriate resources have been purposed for an “approximately 30-kilometer long section of security fence” across Israel’s southeastern border.

The press release notes that Prime Minister Netanyahu commented on the decision in a Monday meeting with the Knesset Foreign Affairs and Defense Committee. The new barrier, he said, “will join the fence that we built along the length of our border with Sinai, which blocked the entry of illegal migrants into Israel and—of course—the various terrorist movements.”

“This is important. It is part of our national security,” said Netanyahu.

He explained that the new fence will span from “Eilat to the site designated for the Timna airport.” The Timna airport, which is currently under construction, is intended to be an alternative airway out of the State should Tel Aviv’s Ben-Gurion airport come under fire. For this reason, the new airport is seen to necessitate strong protection.

Today, Netanyahu commented on the very recent terrorist attacks in Egypt when he went to Jerusalem to visit the four Israelis who had been injured in the checkpoint assaults. According to The Jerusalem Post, he expressed his condolences for the Egyptian victims of the attacks, and stressed that Israel and Egypt were partners in combating the threat of ISIS (translated from Hebrew):

“Terrorism is knocking on our borders,” he said. “Islamic State is not only across from the Golan Heights, it is also in Egypt, across from Rafah, in other words across from our borders,” he said. “And we are together with Egypt and many other states in the Middle East and the world in the struggle against extreme Islamic terrorism.”

“Islamist terror is being guided by Iran—the extremist Shiites; ISIS, the extremist Sunnis; and as other factions such as Hamas.”

Related: Kerry Links Rise of ISIS With Failed Peace Talks