Egypt instructed all of its airlines to avoid Iranian air space for a three-hour period in the early morning on Thursday amid tension between Israel and Iran.

The NOTAM, a safety notice provided to pilots on Wednesday, said the instruction would be in effect from 0100 to 0400 GMT. It provided no further details as to why the notice was issued.

"All Egyptian carriers shall avoid overflying Tehran (Flight information Region) FIR. No flight plan will be accepted overflying such territory," the notice said, referring to the three-hour period provided.

An Egyptian official was quoted by the state-affiliated Al Qahera News TV as saying that the Iranian authorities said to avoid flying in Iranian airspace because of "military exercises."

"Based on a report from Iranian authorities to all civil aviation companies, flights over Iranian airspace are to be avoided," the unnamed official was quoted as saying.

Many airlines are revising their schedules to avoid Iranian and Lebanese airspace while also calling off flights to Israel and Lebanon as many fear a possible broader conflict after the killing of senior members of militant groups Hamas and Hezbollah.

"Such a NOTAM from Egypt is very unusual. It is possible that this is an indicator of an Iranian response to Israel, and in turn a potentially large set of air space disruptions - at the same time, there may be another reason," OPSGROUP, a membership-based organisation that shares flight risk information, said.

On Sunday, Jordanian authorities asked all airlines landing at its airports to carry 45 minutes' worth of extra fuel.

Countries in the region, including Jordan, closed their airspace earlier this year amidst aerial attacks on Israel.