Isis jihadists are carrying out more suicide bombings on civilian targets and other mass attacks as their conventional military powers wane, according to a study of their tactics.
Mass attacks by Isis (Islamic State) rose sharply in the first three months of the year in Syria and Iraq, according to the military consultancy IHS.
The shift is part of a strategy the group has used to bolster its faltering position in both Iraq and Syria.
In another development, Sky News claimed to have evidence Isis was colluding with the Assad regime to limit its losses.
Documents backed by interviews with Isis defectors were said to show that the regime's recapture of Palmyra was actively facilitated by the jihadists, who were allowed to pull out their heavy weapons and withdraw.
Separately, the chief spokesman for the US-led coalition against Isis told the Daily Telegraph it was now clear Isis was "losing" its war, suffering reverses on all fronts on the battlefield even as its ambitions to run a functioning state disintegrated under allied bombing.
It has lost 40 per cent of the territory it controlled in Iraq, but has turned to suicide bombs instead to prove it is still a force to be reckoned with.
Three bombs in and around Baghdad killed 14 people including 11 Shia pilgrims yesterday, a day after a double car bombing of the southern Iraqi city of Samawah killed 31 people.
"The group is resorting more and more to mass-casualty violence as it comes under heavy pressure from multiple angles," said Matthew Henman, of IHS Jane's terrorism and insurgency centre.
Coalition leaders - as well as Iranian and Syrian regime officials - say they believe Isis' "caliphate" is now on the decline.
It is having difficulty keeping electricity and water supplies running as it runs out of cash to pay salaries.
Colonel Steve Warren, spokesman for the US-led coalition, said he believed that the number of Isis fighters being killed was now higher than the "replenishment rate" as foreign fighters were stopped from joining the fray.
Coalition strategy has been to try to push Isis back on all major fronts slowly rather than achieve swift victories in particular areas.
The IHS report found that in response, Isis had increased its attack rate by more than 16 per cent in the first three months of this year over the last quarter of 2015 - killing 2150 people, a rise of 44 per cent.
Henman said much of the increase was civilian. "Wherever you have a situation where they are taking losses they respond with these big mass attacks."