Europe could witness retaliatory attacks by Isis sympathisers, should reports claiming the group's leader has been killed are true, a security analyst has told IBTimes UK.

Counter-terrorism expert David Otto issued the warning as Russia announced on Friday (16 June) it is investigating whether one of its air strikes targeting a meeting of Isis senior members in Raqqa, Syria, on 28 May killed Abu Bakr al-Baghdadi.

"According to information that is being checked through various channels, Isis leader Ibrahim Abu-Bakr al-Baghdadi, who was killed as a result of the strike, was also present at the meeting," the ministry of defence said in a statement, quoted by Russian media.

Shortly after, a US-led coalition battling Isis in Syria told Reuters it was not able to confirm the report. "We cannot confirm," coalition spokesman Colonel John Dorrian was quoted as saying.

Referring to the fact that the UK security service, MI5, was on high alert in 2015 as it feared revenge attacks by Isis fanatics after a British-Arab fighter known as "Jihadi John" was reportedly killed in a drone strike in Raqqa, Otto said: "What is certainly true is that Baghdadi 's death will wake up sleeper cells all over Europe as an immediate reaction to his demise.

"Russia would be the immediate option for target, but Isis would not want to be predictable," he continued.

"Random and disorganised attacks against soft and hard targets using improvised weapons will surely be common by those who are inspired by his [Baghdadi 's] leadership."

The Russian embassy in London declined to comment, while the Ministry of Defence in Russia could not be reached for a comment.

Likewise, the Home Office declined to comment on the speculations made by Otto, and referred to a statement by Prime Minister Theresa May issued in the aftermath of the London Bridge terror attack that reflects the UK's current position on counter terrorism.

"Since the emergence of the threat from Islamist-inspired terrorism, our country has made significant progress in disrupting plots and protecting the public," May said in the statement. "But it is time to say enough is enough. Everybody needs to go about their lives as they normally would. Our society should continue to function in accordance with our values. But when it comes to taking on extremism and terrorism, things need to change.

"As a country, our response must be as it has always been when we have been confronted by violence. We must come together, we must pull together, and united we will take on and defeat our enemies," the statement continued.

The London Bridge attack in June was the third to occur on British soil in the recent months. Isis claimed responsibility for all the three attacks.

The current threat level for international terrorism in the UK is "severe", meaning that an attack is highly likely.

This is not the first time that Baghdadi, who has rarely made any public appearance since announcing the creation of Isis in 2014, has been reported dead.

In the most recent instance, Syrian state TV said earlier in June that Baghdadi had been killed while he was caught in a heavy artillery barrage in Raqqa, which Isis captured in 2014.