The EU begins an ambitious top-to-toe overhaul Tuesday of Mali's ragtag army, far from ready to take the place of foreign troops to defend the West African nation against fresh attacks by Islamist insurgents.

As France prepares to withdraw its 4,000 troops after routing Al Qaeda-linked forces from northern cities, the first of four Malian battalions begins training with battle-hardened European instructors on April 2 as part of a wider effort to bring the army up to scratch as quickly as possible.

"Objectively, it must be entirely rebuilt," said French General Francois Lecointre, who heads the European Union Training Mission in Mali (EUTM).

Underpaid, ill-equipped and riven by divisions, Mali's armed forces fell apart last year when well-armed Islamist extremists seized the country's vast northern reaches, imposing Sharia law and terrorising locals.

Today no one knows exactly how many soldiers are left, probably around 6,000 -- about half of which will train with the EUTM over the next year.

"The Malian authorities are well aware of the need to reconstruct the army, very aware that Mali almost disappeared due to the failings of the institution," said General Lecointre.

Class is at a dusty green-shuttered military academy 60 kilometres (40 miles) from the capital, Bamako, its grounds now packed with rows of EU-supplied troop transport vehicles, a field hospital, tents, and trunk-loads of equipment.

After 10 weeks of training, the first 670 Malians are expected to be ready for combat by end June/early July and deployed to northern Mali, where French and Chadian troops are still on the lookout for pockets of jihadist fighters.

The French are to hand over to an African force of 6,300 likely to come under a UN mandate in the coming weeks. But UN leader Ban Ki-Moon said last week that up to 11,200 troops were needed as well as a second "parallel" force.

While mission commander Lecointre expects the last batch of Malian soldiers to graduate in early 2014, he says the EUTM -- running on a budget of 12.3 million euros -- may have to be extended.

Speaking in Bamako, Mali Defence Minister Yamoussa Camara deemed the 15-month mission "too short" but said it "will enable the training of a core of instructors who will be able to continue training others."

A major issue, according to Lecointre, is the army's poor and "heterogenous" equipment, made up of materiel donated by richer nations over two decades.

"Mali accepted equipment from any country offering but it doesn't function as a whole and often can be either obsolete or over-sophisticated."

EU nations were ready to donate equipment but too often "are inclined to give equipment they no longer want, whilst we are seeking above all to avoid receiving a patchwork of weaponry," he added.

The bigger problem however is the army's lack of a clear hierarchy and chain of command, with no "esprit de corps". "The army is very unstructured," Lecointre said, with soldiers more often than not banding together for one-off missions and not training.

A total 23 EU nations are taking part in the 550-strong EU mission, including 200 trainers, a protection force of 150, another 150 providing medical and logistical support, and 50 administrative staff.

France, which sent troops to its former colony in January to block an advance on the capital by the extremists, is the lead country in the mission, followed by Germany, Spain, the Czech Republic, Britain and Belgium. Lithuania is taking part in such an operation for the first time.

In February, the EUTM sent a score of officers to Bamako to take stock of the state of the armed forces. A plan was submitted to the local authorities in March on how to rebuild the army which will also be drilled in relations with civil society and protection of human rights.

Once trained, each of the four Mali battalions will have a unified command with an infantry-mobile core, backed by artillery and engineering, and a logistics component.