[An Islamic State fighter gestures while being held prisoner with fellow fighters under Democratic Forces of Syria fighters as they ride a pick-up truck near al-Shadadi town, Hasaka countryside, Syria, February 18, 2016. REUTERS/Rodi Said]Thomson Reuters LONDON (Reuters) - U.S. estimates of the number of Islamic State fighters in Iraq and Syria have been reduced while cuts in their pay are evidence they are on the defensive, a spokesman for the U.S.-led coalition fighting the group said on Monday. But the task of defeating Islamic State is complicated by Russian air strikes in Syria which are 90 percent targeted at opposition fighters and not at the jihadist group, U.S. Army Colonel Steve Warren said. Warren said increases in forced conscription, the recruitment of child soldiers and the use of elite fighters in common units were all evidence that Islamic State was seeing a slowing in the influx of foreign fighters. "We believe that Daesh is now beginning to lose. We see them in a defensive crouch," Warren told reporters in London, using an Arabic acronym for Islamic State. U.S. intelligence estimates of the number of Islamic State fighters, which for the first 17 months of coalition operations ranged from 19,000 to 31,000, had been revised to 20,000 to 25,000 - a level he said the group would struggle to maintain. "They have been able to replenish their forces at roughly the same rate as we've been able to kill their forces. That's hard to sustain," he said. Warren said that until recently the average local Islamic State fighter was paid about $400 a month, while foreign fighters, who tended to be "better" because they were more committed and fanatical, were on $600 to $800 a month. However, recent announcements by the group and other evidence suggested that common fighters' pay had been cut by half, while it had also reduced pay for the foreign recruits, though perhaps not by such a large proportion, he said. RUSSIANS "RECKLESS AND IRRESPONSIBLE" Warren said the group had lost 40 percent of the territory it once controlled in Iraq, and 10 percent in Syria, where the coalition's job was much harder, partly due to the Russian air strikes. "The Russians have said they're here to fight terrorists, they're here to fight Daesh. We've seen very little evidence to support that. About 90 percent of Russian air strikes have been against the opposition, not against Daesh," he said. [A man carries an injured woman in a site hit by what activists said were airstrikes carried out by the Russian air force in the rebel-controlled area of Maaret al-Numan town in Idlib province, Syria, January 9, 2016.]Thomson Reuters "The Russians conduct their air strikes using imprecise methods. I find them reckless and irresponsible. They simply drop dumb bombs out of the back their aircraft," he said, adding that the coalition believed the Russians had used cluster bombs. Asked about efforts to build up Syrian forces on the ground to fight Islamic State, Warren contrasted the fighting in the northwest corner of the country with the conflict further east, near the Islamic State stronghold of Raqqa. In the northwest, he said the large number of groups operating made it harder for the coalition to generate a "meaningful ground force" there. But in the strip of land from the town of Kobani to the Iraqi border, the coalition-backed Kurdish YPG group and allies were in control and beginning to drive south toward Raqqa city. In Syria's northeastern province of Hasaka he highlighted the battle for al-Shadadi, a crossroads town east of Raqqa controlled by 400 to 600 Islamic State fighters, which the Syrian Observatory for Human Rights said on Friday had been captured by forces including the YPG. "When we're able to seize that it's yet another piece of the supply lines into Raqqa that becomes seized," he said. (Editing by Dominic Evans) NOW WATCH: An AT&T spokesperson and former refugee is now helping Syrian refugees in Greece