TIMBUKTU, Mali (AP) — One of the last things the bearded fighters did before leaving this city was to drive to the market where traders lay their carpets out in the sand.

The al-Qaida extremists bypassed the brightly colored, high-end synthetic floor coverings and stopped their pickup truck in front of a man selling more modest mats woven from desert grass, priced at $1.40 apiece. There they bought two bales of 25 mats each, and asked him to bundle them on top of the car, along with a stack of sticks.

"It's the first time someone has bought such a large amount," said the mat seller, Leitny Cisse al-Djoumat. "They didn't explain why they wanted so many."

Military officials can tell why: The fighters are stretching the mats across the tops of their cars on poles to form natural carports, so that drones cannot detect them from the air.

The instruction to camouflage cars is one of 22 tips on how to avoid drones, listed on a document left behind by the Islamic extremists as they fled northern Mali from a French military intervention last month. A Xeroxed copy of the document, which was first published on a jihadist forum two years ago, was found by The Associated Press in a manila envelope on the floor of a building here occupied by al-Qaida of the Islamic Maghreb.

The tipsheet reflects how al-Qaida's chapter in North Africa anticipated a military intervention that would make use of drones, as the battleground in the war on terror worldwide is shifting from boots on the ground to unmanned planes in the air. The presence of the document in Mali, first authored by a Yemeni, also shows the coordination between al-Qaida chapters, which security experts have called a source of increasing concern.

"This new document... shows we are no longer dealing with an isolated local problem, but with an enemy which is reaching across continents to share advice," said Bruce Riedel, a 30-year veteran of the CIA, now the director of the Intelligence Project at the Brookings Institution.

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The tips in the document range from the broad (No. 7, hide from being directly or indirectly spotted, especially at night) to the specific (No 18, formation of fake gatherings, for example by using dolls and statues placed outside false ditches to mislead the enemy.) The use of the mats appears to be a West African twist on No. 3, which advises camouflaging the tops of cars and the roofs of buildings, possibly by spreading reflective glass.

While some of the tips are outdated or far-fetched, taken together, they suggest the Islamists in Mali are responding to the threat of drones with sound, common-sense advice that may help them to melt into the desert in between attacks, leaving barely a trace.

"These are not dumb techniques. It shows that they are acting pretty astutely," said Col. Cedric Leighton, a 26-year-veteran of the United States Air Force, who helped set up the Predator drone program, which later tracked Osama bin Laden in Afghanistan. "What it does is, it buys them a little bit more time — and in this conflict, time is key. And they will use it to move away from an area, from a bombing raid, and do it very quickly."

The success of some of the tips will depend on the circumstances and the model of drones used, Leighton said. For example, from the air, where perceptions of depth become obfuscated, an imagery sensor would interpret a mat stretched over the top of a car as one lying on the ground, concealing the vehicle.

New models of drones, such as the Harfung used by the French or the MQ-9 "Reaper," sometimes have infrared sensors that can pick up the heat signature of a car whose engine has just been shut off. However, even an infrared sensor would have trouble detecting a car left under a mat tent overnight, so that its temperature is the same as on the surrounding ground, Leighton said.

Unarmed drones are already being used by the French in Mali to collect intelligence on al-Qaida groups, and U.S. officials have said plans are underway to establish a new drone base in northwestern Africa. The U.S. recently signed a "status of forces agreement" with Niger, one of the nations bordering Mali, suggesting the drone base may be situated there and would be primarily used to gather intelligence to help the French.

The author of the tipsheet found in Timbuktu is Abdallah bin Muhammad, the nom de guerre for a senior commander of al-Qaida in the Arabian Peninsula, the Yemen-based branch of the terror network. The document was first published in Arabic on an extremist website on June 2, 2011, a month after bin Laden's death, according to Mathieu Guidere, a professor at the University of Toulouse. Guidere runs a database of statements by extremist groups, including al-Qaida in the Islamic Maghreb, and he reviewed and authenticated the document found by the AP.

The tipsheet is still little known, if at all, in English, though it has been republished at least three times in Arabic on other jihadist forums after drone strikes took out U.S.-born cleric Anwar al-Awlaki in Yemen in September 2011 and al-Qaida second-in-command Abu Yahya al-Libi in Pakistan in June 2012. It was most recently issued two weeks ago on another extremist website after plans for the possible U.S. drone base in Niger began surfacing, Guidere said.

"This document supports the fact that they knew there are secret U.S. bases for drones, and were preparing themselves," he said. "They were thinking about this issue for a long time."

The idea of hiding under trees to avoid drones, which is tip No. 10, appears to be coming from the highest levels of the terror network. In a letter written by bin Laden and first published by the U.S. Center for Combating Terrorism, the terror mastermind instructs his followers to deliver a message to Abdelmalek Droukdel, the head of al-Qaida in the Islamic Maghreb, whose fighters have been active in Mali for at least a decade.

"I want the brothers in the Islamic Maghreb to know that planting trees helps the mujahedeen and gives them cover," bin Laden writes in the missive. "Trees will give the mujahedeen the freedom to move around especially if the enemy sends spying aircrafts to the area."

Hiding under trees is exactly what the al-Qaida fighters did in Mali, according to residents in Diabaly, the last town they took before the French stemmed their advance last month. Just after French warplanes incinerated rebel cars that had been left outside, the fighters began to commandeer houses with large mango trees and park their four-by-fours in the shade of their rubbery leaves.

Hamidou Sissouma, a schoolteacher, said the Islamists chose his house because of its generous trees, and rammed their trucks through his earthen wall to drive right into his courtyard. Another resident showed the gash the occupiers had made in his mango tree by parking their pickup too close to the trunk.

In Timbuktu also, fighters hid their cars under trees, and disembarked from them in a hurry when they were being chased, in accordance with tip No. 13.

Moustapha al-Housseini, an appliance repairman, was outside his shop fixing a client's broken radio on the day the aerial bombardments began. He said he heard the sound of the planes and saw the Islamists at almost the same moment. Abou Zeid, the senior al-Qaida emir in the region, rushed to jam his car under a pair of tamarind trees outside the store.

"He and his men got out of the car and dove under the awning," said al-Housseini. "As for what I did? Me and my employees? We also ran. As fast as we could."

Along with the grass mats, the al-Qaida men in Mali made creative use of another natural resource to hide their cars: Mud.

Asse Ag Imahalit, a gardener at a building in Timbuktu, said he was at first puzzled to see that the fighters sleeping inside the compound sent for large bags of sugar every day. Then, he said, he observed them mixing the sugar with dirt, adding water and using the sticky mixture to "paint" their cars. Residents said the cars of the al-Qaida fighters are permanently covered in mud.

The drone tipsheet, discovered in the regional tax department occupied by Abou Zeid, shows how familiar al-Qaida has become with drone attacks, which have allowed the U.S. to take out senior leaders in the terrorist group without a messy ground battle. The preface and epilogue of the tipsheet make it clear that al-Qaida well realizes the advantages of drones: They are relatively cheap in terms of money and lives, alleviating "the pressure of American public opinion."

Ironically, the first drone attack on an al-Qaida figure in 2002 took out the head of the branch in Yemen — the same branch that authored the document found in Mali, according to Riedel. Drones began to be used in Iraq in 2006 and in Pakistan in 2007, but it wasn't until 2009 that they became a hallmark of the war on terror, he said.

"Since we do not want to put boots on the ground in places like Mali, they are certain to be the way of the future," he said. "They are already the future."

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Associated Press writers Baba Ahmed in Timbuktu, Mali, Robert Burns in Washington and Dalatou Mamane in Niamey, Niger contributed to this report.

The document can be seen in Arabic and English at http://hosted.ap.org/specials/interactives/_international/_pdfs/al-qaida-papers-drones.pdf.

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Rukmini Callimachi can be reached at www.twitter.com/rcallimachi

Baba Ahmed can be reached at www.twitter.com/babahmed1