* Gao attacks trigger operation to secure Saharan town
* But jihadists not far away, just across Niger River
* Searches, checks sap momentum of hard-charging French
* Local informers lead to arrests, home bomb factory
By the slow-moving Niger River at Gao, the north Malian town retaken by French troops from Islamist rebels last month, men repair fishing nets beside beached pirogues, women wash pots and children splash naked in the muddy water.
The scene looks tranquil enough but the French soldiers and their allied troops from Niger on the riverbank are alert, fingering their weapons and squinting southwest across the water to the village of Kadji, shrouded by eucalyptus trees.
Locals living along the bank have identified Kadji as a hotbed of al Qaeda-allied jihadists who last weekend surprised the French, Malian and Nigerien troops in Gao with two suicide bombings and a daring raid into the heart of the town.
Since Sunday's attack, the French and their African allies have been busy hunting down rebel suspects and dismantling bomb-making factories in the sprawling mud-brick Saharan town in a counter-insurgency operation that is tying them down.
"After Sunday, securing Gao is our priority," said a French officer who, like many involved in the operation, asked not to be identified. "Once we have done this, we will move out of town to help the Malians neutralise these pockets of Islamists."
The house-to-house searches, sandbagging of fixed defensive positions and reliance on tip-offs from locals already have the hallmarks of an arduous counter-guerrilla operation.
The need to secure Gao, hundreds of kilometres behind the French forward lines where commandos are hunting for French hostages believed to be held in rebel mountain hideouts, is robbing momentum from France's five-week-old campaign.
France's military operation which started in Bamako, the southern capital, and drove 1,700 km (1,050 miles) northwards to Tessalit near the Algerian border, initially forced the bulk of the Islamist forces from the main northern towns of Gao and Timbuktu, earning global plaudits for French President Francois Hollande.
The United States and Europe praised a decisive move against Mali-based jihadists threatening international attacks.
But following the recent Gao attacks, French spokesmen are increasingly having to fend off suggestions that the 4,000 French soldiers in Mali could risk getting mired in a long and debilitating war, in a tough and hostile battleground.
"I don't think we can talk for the moment about getting bogged down," French army spokesman Colonel Thierry Burkhard told reporters on Thursday in Paris.
"Bamako-Tessalit, that's like the distance from Paris to Rome," Burkhard said, stressing the speed of the French campaign, which has cost the life of only one French serviceman so far - a helicopter pilot killed early in the operation.
But others see clear "mission-creep" risks in Mali.
"It's very much going to be an insurgency on the ground like we've seen in Iraq and like we've seen in Afghanistan," Canada's Foreign Minister John Baird said on Tuesday, explaining why Canada was not likely to send troops to support the French.
AFTER EUPHORIA, UNEASE
Conscious of the task facing the French to stabilise north Mali, Gao citizens who spent months living alongside Islamist occupiers under the yoke of severe sharia law are coming forward with information on the jihadist gunmen and their arms caches.
"We know the fighters. We are keeping an eye on them. We are ready to denounce them," said Seydou Maiga, speaking beside his riverside hut, in full view of Kadji.
The attention of the French and their African allies is focusing on suspected jihadist hotspots like Kadji. Authorities say Sunday's raiders slipped across the river in canoes while soldiers were distracted at checkpoints by suicide bombers.
A joint French-Nigerien military patrol picks up the latest information on the riverbank from locals such as Maiga.
The informants tell the troops a group of children acting as scouts for the Islamists had slipped across the river by canoe hours earlier, raising fears of fresh rebel infiltrations.
Malian troops convinced the children to lead them to the people they were meant to meet in town. As a result, four youths, suspected collaborators with the insurgents, were arrested in the market, Maiga said.
"We have mobilised residents to inform authorities whenever they see people they don't recognise," Gao Mayor Sadou Diallo told Reuters. He said this early warning system from the local population helped the military to intercept Sunday's raiders before they could carry out more suicide bombings.
The attacks have soured the mood of the town, ending the post-liberation euphoria. Shops have been shuttered and French and African forces have stepped up their patrols, their jeeps and armoured vehicles rumbling through the sandy streets.
At checkpoints outside Gao, jittery soldiers search passengers on buses and check the papers of anyone riding motorbikes, used by Islamists in their suicide attacks.
Around the government army base in town, and other potential targets like checkpoints, civilians have been cutting down trees and shrubs to reduce cover for would-be attackers.
Following a tip-off from locals, French troops on Wednesday made safe homemade explosives found inside a house in Gao, which they said was a bomb-making factory, abandoned by fleeing Islamists when the town was liberated nearly three weeks ago.
Inside, unused shell casings and shreds of a black Islamist flag with Koranic inscriptions in white lay on the floor. Surfaces were littered with tools for making homemade explosives from fertiliser, including an oxygen tank, and utensils for measuring out powder.
"When the Islamists left, we went into the house and inside we found rockets, buckets with wires coming out and bullets," said Mahamadou Kabare, who lived opposite the building.
When Islamist militants swept down through northern Mali last year accompanying a Tuareg separatist revolt, which they later hijacked, hundreds of thousands of people fled their harsh sharia Islamic rule. Tapping into poverty and pockets of fundamentalism, rebels were able to recruit fighters locally.
But many in the occupied towns, while lacking weapons to fight the Islamists, were proud to show passive resistance.
"We burned tyres. We sang the national anthem," said Amadou Sarr, who used to work for aid agencies in Gao but is now a leader of "Gao's Patrollers", whose members take to the streets nightly to protect houses and businesses.
Sarr said that hundreds of people had been identified as suspected Islamists or collaborators by his network. But he said Mali's army and their allies from France and Niger were too thinly stretched to follow up immediately on all the reports.
"They lack the men and the means," he said.
Gao and Timbutku have largely emptied of Arabs and Tuaregs, ethnic groups that made up the bulk of the Tuareg separatist and Islamist rebels. In the days after French and Malian forces retook the northern towns, shops owned by Arabs were looted.
Such acts of vengeance suggest that re-establishing peace and unity before elections expected by July 31 will be an uphill task for Mali's authorities and their French and African allies.
"Those who took up arms against fellow Malians deserve to be crushed," Sarr said. "People talk about reconciliation but we are not ready for it yet."