* Nigerian army to establish 'super camps' in northeast
* Soldiers leaving some towns they protected previously
* New strategy affecting access by aid workers to some areas
By Paul Carsten
ABUJA/MAIDUGURI, Reuters, Sept 16 (Reuters) - When IslamicState gunmen stormed the northeast Nigerian town of Magumeri onthe night of August 21, they had free rein.
Nigerian soldiers had left the town earlier that month undera new strategy of withdrawing to "super camps" that can be moreeasily defended against insurgents the army has been strugglingto contain for a decade.
Unchallenged, the Islamist militants torched a clinic inMagumeri, ransacked government buildings and looted shops beforereturning to another town they had raided that night calledGubio, residents said.
The new military strategy announced by President MuhammaduBuhari in July to concentrate soldiers in big bases is designedto give troops a secure platform from which they can respondquickly to threats in the region and raid militant camps.
People familiar with the military's thinking and securityofficials, however, say the new tactic for fighting IslamicState's West Africa branch and Boko Haram is mainly an attemptto stem casualties.
The military did not respond to requests for more detailsabout its strategy or the impact it will have on the region.
"We strongly believe the days of BH (Boko Haram) movingfreely and passing in between static defensive locations areover," Major General Olusegun Adeniyi, who commands theanti-insurgency operation, told reporters last month.
Boko Haram launched an insurgency in 2009 to overthrow thegovernment and establish an Islamic caliphate. The group, whoseunofficial name means "Western education is forbidden", heldterritory the size of Belgium in 2014 but a multinationaloffensive recaptured much of it the following year.
The group split in 2016 and the faction that has been thegreater threat ever since won the recognition of Islamic State.
The decade of war has killed more than 30,000 civilians andspawned what the United Nations calls one of the world's worsthumanitarian crises, which foreign nations are trying to containwith billions of dollars of aid.
But the crisis shows no sign of abating.
'IT'S A MESS'
The army's withdrawal into large bases has coincided with astring of insurgent raids on newly unprotected towns and hasleft the militants free to set up checkpoints on roads as theyroam more freely across the countryside, according to threebriefing notes from an international aid and developmentorganisation, two security officials and residents.
That has left thousands of civilians without access to aid,according to the briefing notes seen by Reuters.
Soldiers are no longer protecting some key roads, cuttingoff access for humanitarians workers as more of the region fallsunder the sway of the insurgents, aid and security sources said.
"It's a mess, militarily, and a disaster for humanitarianactors," one foreign security official said.
The population of towns being abandoned by the military is acombined 223,000 people, according to one of the aid agencybriefing notes.
The military departures so far have cut off more than100,000 people from aid and if more soldiers go, as many as121,000 other civilians could flee their towns, one aid agencybriefing note said.
"The impact will be one of continued skirmishes - soldiersunder constant strain to deal with the insurgency where IslamicState and Boko Haram dictate the momentum," said JasmineOpperman, a terrorism expert based in South Africa.
It's not yet clear how many "super camps" the army plans toset up, where they will be nor how many soldiers each will hold.
'HERE TO PROTECT YOU'
The new strategy follows a series of setbacks for the armywhich has failed to keep a tight grip on territory it has clawedback since 2015. Last year, insurgents repeatedly overransmaller bases and sent soldiers and tens of thousands of peoplefleeing from larger towns.
Security experts put the military death toll since June 2018at anywhere from hundreds of soldiers to in excess of 1,000.
The military has not released casualty figures but deniesthat many soldiers have been killed.
One security adviser at an international aid organisationsaid a major goal of the new large bases was damage control,rather than going on the offensive.
"It is to consolidate all of the strength in one place toprevent them being overrun every week," the adviser said.
He said the areas vacated were being filled by insurgentsand that would make it harder for the military to re-enter,leaving civilians vulnerable.
Those concerns were echoed by the governor of Borno - thebirthplace of Boko Haram and the state worst hit by theinsurgency. Governor Babagana Umara Zulum told reporters lastmonth that recent attacks were the result of a "serious vacuum"following the withdrawal of soldiers.
Islamic State is also using its newfound freedom to woolocals. Drained by the decade-long conflict, some are open tomoving into areas controlled by the insurgents where life can bemore stable, residents said.
Before hitting Magumeri last month, the militants had passedthrough the town of Gubio, some 40 km (25 miles) to the north.
There, an Islamic State fighter led evening prayers followedby a sermon, according to six residents.
"We are here to protect you, not to harm any one of you,"the IS fighter told residents. "Those with uniforms are yourenemies, and we are here to deal with them and their supporters.You should feel free."
Rather than flee to a government-controlled city such asBorno state's capital Maiduguri, many Gubio residents stayed.(Reporting by Reuters correspondents in Abuja and Maiduguri;additional reporting by Camillus Eboh in Abuja; editing byAlexis Akwagyiram and David Clarke)