Jordan's military Friday denied claims by the Islamic State group to have shot down one of its warplanes which crashed in Syria, after the pilot was captured by the jihadists.

"First indications show that the crash of the Jordanian military plane in the area of the Syrian city of Raqa was not caused by Daesh fire," a military official said using another name for IS.

"But since the wreckage of the plane cannot be reached and since its pilot is not present, we cannot at this moment determine the exact cause of the crash," the official said in remarks published on the army's website.

Maaz al-Kassasbeh, a 26-year-old first lieutenant in the Jordanian air force, was captured by IS on Wednesday after his F-16 jet crashed while on a mission against the jihadists over northern Syria.

The US military has also dismissed the jihadists' claim to have hit the jet with an anti-aircraft missile, saying "evidence clearly suggests that ISIL (IS) did not down the aircraft".

The crash was the first warplane from the US-led coalition lost since air strikes on IS began in Syria in September, and marks a major propaganda victory for the Sunni extremist group.

Jordan is among a number of countries that have joined the air raids against IS.

Coalition warplanes have carried out regular strikes around Raqa, which IS has used as its de facto capital since declaring a "caliphate" in June straddling large parts of Iraq and Syria.