Claims by Iran that is has produced a new domestically-produced fighter jet have been questioned by military experts.

On Tuesday, Iranian state television screened images of President Hassan Rouhani sitting in what was reported as a new "Kowsar" fighter aircraft.

Local media also reported that the plane was a fourth-generation fighter jet that had been designed and manufactured solely by Iranian military experts.

However, international aviation experts have been quick to cast doubt on the claim of pure Iranian technology and have suggested that the design is that of the U.S.-made F-5F jet, first built in the early 1970s. Tehran purchased F-5s from America in 1974, five years before the Iranian revolution.

Joseph Dempsey, a defense and military analysis research associate at the International Institute for Strategic Studies (IISS), took to Twitter to illustrate the comparison.

Speaking to CNBC by telephone Wednesday, his colleague and senior fellow for military aerospace at IISS, Douglas Barrie, agreed that the plane unveiled by Iran appeared to be a two-seater F-5.

Barrie said the idea that the plane was an indigenous creation should be taken with "a massive pinch of salt" but added there could be an element of truth to the manufacture of some new parts.

"The Iranians probably have the industrial capacity to at least make fuselage assemblies for this aircraft. They have obviously been able to make bits of these things," he said.

Barrie added that Iranian engineers may also have upgraded the plane's electronic control system, but that would not have proven particularly difficult given that the original specification hailed from as long ago as the 1960s.

John Sneller, head of aviation at defense consultancy Jane's IHS Markit, also identified the plane as a two-seater F-5F. Speaking to CNBC by phone Wednesday, Sneller said the aircraft shown in images released by Iran had obvious design elements of the U.S.-made plane.

"The markings on the side, particularly the slightly unusual air intakes that slope backwards slightly, are those of the F-5F," he said, adding, "It is all a bit of a giveaway really."

Sneller said he believed Iran is trying to demonstrate that it still has fighter jet capability and that it is also suggesting to international watchers that the aircraft's internal systems have been updated.

He said with pressure coming from the U.S., Israel and Saudi Arabia, leaders in Tehran would also be keen to show their own people that Iran has some way of protecting itself.

"They are developing their own indigenous capability — but that is a long way from designing, certifying, and manufacturing their own aircraft, and that does not look to be the case in this particular set of images that have come out," Sneller said.

The current estimate by Jane's IHS Markit is that Iran has 31 single-seater F-5E jets and 17 two-seater F5-F aircraft in service.

Iran's military had a 2017 budget of $14.1 billion, or 2.5 percent of its gross domestic product (GDP), according to figures supplied by the Stockholm International Peace Research Institute (SIPRI).