Although Israeli-Egyptian security cooperation has never been closer, Egypt refused Israeli offers of medical assistance for the tourists wounded when their bus was blown up by Islamic extremists Sunday afternoon, just inside Egyptian territory at the Taba border crossing.

Three Korean tourists and the Egyptian bus driver were killed in the bombing, and at least twelve passengers were seriously injured. The bomb was placed under the driver’s seat and detonated by remote control as the vehicle neared the crossing into Israel.

More than two dozen Israeli ambulances were despatched to the crossing immediately after the bombing — which took place just across the border and was audible inside Israel — but the Egyptian authorities refused Israel’s offers of assistance. Israeli “emergency forces were ready within minutes,” the local Israeli Magen David Adom emergency chief said.

Some reports said the injured were eventually brought to a hospital at the Egyptian resort of Sharm e-Sheikh a full three hours after the blast. Other reports said not all of the injured had been evacuated by evening. Eilat’s Yoseftal Medical Center is a few minutes’ drive from the Taba crossing.

No Israelis were among the casualties, an Israeli police spokesman said.

Israel also offered assistance in investigating the bombing but that offer was not immediately accepted either, Israeli sources said on Sunday night. This, despite the fact that security cooperation between Israel and the Egyptian leadership under military strongman Abdel-Fattah el-Sissi “has never been closer,” according to Israeli military sources.

Initial investigation indicated that the bomb was planted under the driver’s seat of the tourist bus when it made a stop en route to Taba at the resort town of Nuweiba. The bomb was detonated by remote control, as the bus waited near the Taba Hilton hotel to obtain permission to cross into Israel.

Security arrangements at the crossing are such that the terrorists would not have been able to carry out the attack at the Israeli side of the border or inside Israel, security sources said Sunday night without elaboration.

The IDF’s Southern Command’s former chief of staff, Brig. Gen. (res.) Tzvika Fogel, warned that Sinai terror was likely to continue, and was a response to the perception among terror groups that their opponents were growing in strength. “The terror initiatives won’t stop surprising us as long as the Egyptians and the Palestinian Authority will continue to grow stronger in the eyes of those who are carrying out the terror,” said Fogel.

Israel’s Channel 2 news reported that dozens of Israelis were vacationing at the Taba Hilton at the time of the blast. Several of them, and other Israeli tourists in Egypt, immediately sought to return to Israel. By evening, Israel had reopened its facilities at the Taba crossing to enable them to cross back into Israel. Egypt later reopened the crossing as well.

In 2004, a bomb blast at the Hilton killed 31 people. The hotel, which houses a casino, is about 100 meters from the border.

Officials said the tourist bus had arrived at Taba from the ancient Greek Orthodox monastery of St. Catherine in central Sinai. The bus, filled with 32 Korean Christian pilgrims, had started its journey in Cairo, passed through St. Catherine, stopped briefly at Nuweiba and was on its way to Eilat when the bomb exploded shortly before it reached the border.

Ansar Bayt al-Maqdis, an al-Qaeda affiliated terrorist organization, reportedly claimed responsibility for the attack, various Arabic-language media outlets reported.

The group said on Twitter that it would continue to attack Egypt’s economy, tourism and its military commanders, Israel Radio reported.

The Sinai-based al-Qaeda-linked group was also responsible for a handful of terror attacks throughout Egypt and for several Grad rockets launched at Eilat over the past month from across the border.

Ansar Bayt al-Maqdis is reportedly holed up in the mountainous center of the arid peninsula, an area the Egyptian military has been loath to approach in its ongoing battle with terror groups in the increasingly turbulent Strip.

Some Egyptian media reports, nonetheless, blamed Hamas, the Islamist organization that rules the Gaza Strip. El-Sissi has been relentlessly closing smuggling routes between the Sinai and Gaza, in part because he blames Hamas for direct involvement in terrorism in the Sinai. Egyptian officials in recent weeks have vowed to take on Hamas once they have defeated Sinai-based terrorism.

A picture from the scene showed a burnt-out husk of a bus on the side of the road.