Security and military agencies in the frontline of the war against Isis are coming to the conclusion that Abu Bakr al-Baghdadi may well have been killed two months ago in an air strike on the outskirts of Raqqa.

Russia, which carried out the attack, initially said that it was investigating whether the Isis chief had died when two of its warplanes hit a meeting at the southern edge of the capital of the “caliphate”. Up to 300 fighters and 30 field commanders were also said to have been killed in the ten minute missile salvo fired from two warplanes on 28 May.

There is hesitation among officials to claim the death of Baghdadi. He had been killed off in the past only to resurface later. However, towards the end of last month the Russian deputy foreign minister, Oleg Syromolotov, said it was “highly likely that he was eliminated in an air strike” and senior figures in the Russian military are now said to be convinced that was the case.

At the same time, Turkish officials say that they are receiving persistent reports that the head of Isis is dead. Ankara and Moscow have selectively worked together in Syria and the Russians are thought to have passed information to the Turks which led to the killing of Abdurakhmon Uzbeki, who organised the bombing of an Istanbul nightclub on New Year’s Eve. Uzbeki, a confidant of Baghdadi, was shot down in a raid by US Special Forces.

The British based monitoring group, the Syrian Observatory for Human Rights, said on Tuesday that it was convinced that Baghdadi had been killed. Its director, Rami Abdulrahman, said: “We have confirmed information from leaders, including one of first rank who is Syrian, in the Islamic State in the eastern countryside of Deir al-Zor.”

Syrian opposition fighters and activists on the Turkey-Syria border said they had heard that Isis had confirmed the death at the town of Tal Afar and stated that a successor will be announced soon. This follows, they say, a lifting of a ban by the group on discussing the whereabouts of its leader, something which, it is claimed, resulted in public lashing in the past. There is, however, no corroboration of this.

In Iraq, Colonel Ryan Dillon, spokesman for the US military, said he could not confirm that Baghdadi had been killed: “We hope it is true and we strongly advise Isis to implement a strong line of succession. It will be needed.”

In pictures: Isis' weapons factories Show all 11 1 /11 In pictures: Isis' weapons factories In pictures: Isis' weapons factories A mortar round fin manufactured by Isis in Gogjali, Mosul, November 2016 Conflict Armament Research In pictures: Isis' weapons factories Isis rocket components discovered in Gogjali, Mosul, Iraq in November 2016 Conflict Armament Research In pictures: Isis' weapons factories Isis mortars discovered near Karamlais, Iraq, in November 2016 CAR In pictures: Isis' weapons factories An Isis rocket launch frame in Qaraqosh, November 2016 Conflict Armament Research In pictures: Isis' weapons factories A memo from Isis' COSQC on quality control at a manufacturing facility in Gogjali, Mosul, November 2016 Conflict Armament Research In pictures: Isis' weapons factories Electrically-operated initiators manufactured by Isis in forces Gogjali, Mosul, November 2016 Conflict Armament Research In pictures: Isis' weapons factories Isis mortar tubes at a manufacturing facility in Karamlais, November 2016 Conflict Armament Research In pictures: Isis' weapons factories An Isis mortar production facility discovered in Gogjali, Mosul, in November 2016 Conflict Armament Research In pictures: Isis' weapons factories An Isis weapons manufacturing facilities near Mosul in November 2016 Conflict Armament Research In pictures: Isis' weapons factories Stocks of French-manufactured Sorbitol, Latvian potassium nitrate and Lebanese sugar at an Isis weapons factory in Iraq Conflict Armament Research In pictures: Isis' weapons factories A destroyed Isis weapons facility in Qaraqosh, Iraq, November 2016 Conflict Armament Research

A senior Turkish official commented: “We have been hearing from a number of sources that Baghdadi may well have died. The Russians seem to think that is the case and we think some people in Daesh (Isis) also think that is the case. We have not yet seen any proof of this ourselves. But it is certainly a strong possibility, more so than it was even a few weeks ago.”

The Isis meeting attacked by the Russian aircraft, a SU-34 and SU-35, was being held, it is believed, to discuss plans of delaying the enemy with the use of suicide bombers and IEDs (improvised explosive devices) while escape routes were organised for the leadership. Up to six senior leaders, it has been claimed, were killed including Abu-al-Khadzhi al-Mysri, Ibrahim Haef al-Khadi and Suleiman al-Shuauakh, the group’s security chief.

The only public appearance of Baghdadi took place when he declared the creation of a caliphate during a sermon in Mosul in June 2014. He was believed to have been in the city before Iraqi forces, backed by the Americans, began the offensive to retake the city. Since then his whereabouts have been unknown, with reports that he was hiding in the desert rather than in any urban location.