"We're aware of the alert," the official told Ahram Online by phone. "Israel usually informs us before it issues alerts; these are the procedures."

According to the official and other informed sources, the threat is "to be expected" in light of an Israeli air strike in the Gaza Strip on Saturday that killed the commander of Jihadist group Tawhid wal Jihad.

The security official said that, since Saturday, security measures in the area had been "stepped up."

Other government sources, meanwhile, acknowledge that intelligence exchanges between Egypt and Israel – as between Egypt and Palestinian resistance movement Hamas, which governs the Gaza Strip – have been ongoing in recent days.

The latest Israeli air strike on Gaza "was a significant operation; it's only expected that Al-Tawhid wal Jihad would attempt to retaliate," military-political commentator Mohamed Abdel-Salam told Ahram Online.

He added: "It would be very tough for the Jihadists to operate from Gaza given the fact that Gaza is under the very tight control of Hamas; retaliatory attacks from Sinai would be easier."

Another security official told Ahram Online: "I'm not ruling anything out, but – given the ongoing military operation in Sinai – one should hope that things are being brought under control there."

As of early august, the army – under the command of recently appointed Defence Minister Abdel-Fattah Al-Sissi – has been combing Sinai for militant Jihadists.

According to a military source, the operation "is progressing well, but we're trying to clean up a mess that has been ignored for at least ten years. It's a job that requires time and effort, especially that we're being very careful to avoid collateral damage."

Assessments of the Sinai operation's impact, meanwhile, remain debatable.  Relevant state bodies say that significant progress has been made, at least in terms of deterrence. Some foreign diplomats in Cairo, however, suggest it is still too early to say that alleged Sinai-based militant networks have been deterred.

"Maybe they've been thrown on the defensive. They are certainly not as free as they used to be. But even Egyptian officials do not say that the situation has been brought under control," said one Cairo-based European diplomat.

Egypt, according to diplomatic sources, is constantly receiving queries about the situation in Sinai. The same sources say that Cairo is showing transparency in this regard by informing all concerned parties that progress is being made and that coordination remains underway both with Israel and Hamas in Gaza.

"The trouble is that Hamas is not really in full control of Gaza; we know there are parts of the strip that are almost completely under the control of the Jihadists," the same diplomat said.

Egyptian officials say Israel is intensifying its intelligence operations in southern Gaza, where Jihadist groups are alleged to be active.

"In fact, there are clear signs of serious Israeli infiltration of these groups at the highest levels – this is the only way to explain the surgical operations that Israel has been conducting recently," said Abdel-Salam.

Some concerned Egyptian officials say that the ongoing military operation in Sinai requires better military hardware – a notion, they add, that Israel is perennially uncomfortable with.

According to the terms of the 1979 peace treaty between the two countries, Egypt is only allowed a very limited police and military presence in the part of Sinai closest to Israel.

There have been frequent Egyptian calls to revise the treaty's terms, but Israel has consistently rejected any modification of the current arrangement.  

Egyptian Presidential spokesman Yasser Ali recently acknowledged that no amendments to the treaty were likely to be negotiated with Israel any time soon.

"We're doing the best we can and are coordinating daily with Israel," said the military source. "But Israel will always complain under any circumstances."