TEHRAN — Iran’s air defense systems continue to demonstrate significant improvements since the 12-day war in June, with the military announcing that it has downed a fourth American fighter jet within the span of six days.

According to a statement from the Islamic Revolution Guard Corps (IRGC), an American F-15 fighter jet crashed along Iran’s southwestern borders after being intercepted by the country’s air defense systems.

“An invading American two-seat, multi-role strike fighter, an F-15E Strike Eagle, was successfully targeted by the IRGC Aerospace Force’s new air defense systems in the early hours of Wednesday and crashed along the southwestern borders of Iran,” the statement said. It did not comment on the fate of the two pilots.

Previously, Iran reported downing three F-15s before they could enter Iranian airspace. Those warplanes crashed on Kuwaiti soil, and their pilots ejected, though the American military claimed they were brought down by what it described as “apparent” friendly fire.

There are also unverified reports of a fifth F-15 being downed in western Iran. The Iranian Armed Forces have not yet confirmed that incident.

The downing of crewed American warplanes has not occurred since the Kosovo War 27 years ago.

Iranian air defense units have also carried out several other notable interceptions since February 28. They have downed around 30 Hermes drones and four MQ-9 drones, according to statements by the IRGC. These two types of drones are considered among the most advanced in the world.

Iran has demonstrated marked improvement in its interception capabilities since the 12-day war eight months ago.