The tide is beginning to turn on the Islamic State group, analysts say, with the jihadists losing ground in Iraq and only able to hold on to their positions in Syria.

Harassed by air strikes and facing better coordination among their opponents, IS fighters have suffered a string of defeats in Iraq and had to retreat from some areas they had conquered in June and the following months.

In November alone, the jihadists pulled back from the key battleground of Jurf al-Sakhr south of Baghdad, lost the northern town of Baiji and lifted their siege of a nearby refinery.

In the east, they were also ousted from one of the country's largest dams in Adhaim and two towns near the border with Iran.

In Kobane, a Kurdish town on Syria's border with Turkey, weeks of fighting and suicide attacks have cost IS dear in manpower and failed to break the defenses of Kurdish fighters.

"The anti-IS war effort is beginning to show more concrete results across a diverse set of battlefields," said Ayham Kamel, an analyst with the Eurasia Group.

Foreign jets and drones strike jihadist targets in Iraq and Syria dozens of times a week, smashing IS equipment and safe houses and disrupting its movements and command structure.

The jihadist group and its supporters deny that momentum is swinging, but a string of defeats, or at least thwarted assaults, suggest IS' military aura is fading.

The jihadists had thrived in Iraq's grey areas claimed by both the government and the autonomous Kurds, but a thaw in relations has led to better coordination and energized the anti-IS fightback.

Saadiyah and Jalawla are two towns in such areas, and their recapture last week confirmed that the eastern borders of IS supremo Abu Bakr al-Baghdadi's self-proclaimed "caliphate" had begun to roll back.

"In areas where you've had the peshmerga pushing down from the north and the Iraqi army pushing up from the south, that's been tactically a good way of operating," a senior Western diplomat said.

"I think a strategic decision has been taken to liberate the eastern side of the country and then move towards the west."

In a brief published on Monday, the Soufan Group think tank argued that IS, whose motto is "Remaining and Expanding", was now "remaining but slowly contracting."

John Drake, an analyst with the AKE Group, said however that the victories notched up in Iraq may have been some of the lowest-hanging fruit.

He said the alliance of army, Kurdish peshmerga, Sunni tribal fighters and Shiite militia would soon have tougher nuts to crack if the jihadists "retreat from parts of northern Salaheddin (province) to regroup in Mosul and urban Anbar province."

The fear of causing civilian casualties has meant that IS strongholds in Mosul, Tikrit and Fallujah have been largely spared by the hundreds of air strikes carried out since August.

The battle for Kobane, of limited strategic importance but so publicized that its outcome will have a significant impact, has killed hundreds of IS fighters, according to the Syrian Observatory for Human Rights.

The group's director, Rami Abdel Rahman, said the jihadists' offensives in the east of Homs province had also been blunted by Syrian regime forces.

"IS does not enjoy real popular support in the areas it holds. The only reason it is in control is because it has terrorized the people into submission," he said.

Some observers interpreted the graphic escalation in a propaganda video released by IS last month and showing mass beheadings in slow motion as a sign of desperation.

In a rare audio recording, Baghdadi himself sounded at pains to reassure his followers that IS was still gaining strength and on the path to victory.

Analysts say IS could soon be on the back foot in their Iraqi stronghold of Anbar, a vast region traversed by the Euphrates and parts of which were under insurgent control long before June.

"The federal government -- together with (Sunni) tribes, Shiite militias and international airpower -- is about to make Anbar its next priority," said Michael Knights of the Washington Institute.

He predicted that the huge desert expanse bordering Saudi Arabia, Jordan and Syria would be hard to secure but that IS could be forced out of the main cities along the river.

The incompetence and corruption that has characterized the federal army in recent months will take time to eradicate, and taking back large Sunni cities remains a daunting challenge for the government.

"I do not think that there's a quick fix for the security crisis in Anbar," Kamel said. "Forming the right alliances with tribes and arming Sunni units will take significant time to show concrete results."

The jihadists have responded to the government's military resurgence by attempting to light new fires across the country.

But even in Anbar, an attack in Ramadi last month has so far failed to break a desperate stand for the provincial capital by pro-government forces.