Calais -- Sleeping under bridges or hiding in the dunes, dozens of Afghans are back in Calais and still bent on crossing to Britain, one week after they were rounded up by French riot police.

Some 276 migrants were detained last Monday when police bulldozed the squalid "Jungle" migrant camp, but judges ordered half to be freed over breaches of their rights, leaving many to drift back to the northern city.

Of the 138 adults shipped to detention centres across France, 95 have been released into legal limbo, the Cimade aid group said Monday, while officials said 28 of the 125 minors taken to youth detention centres had been released.

Yussuf, Asseb, and Muramad, three Afghan Pashtun teenagers picked up in the notorious "Jungle," were back in Calais within a day of their release, setting up camp behind a clump of bushes on a quayside near the town hall.

"Police they leave us in Nimes, minimum one thousand kilometres from Calais. We come back by train," the 14-year-old Yussuf told AFP Monday in faltering English. "They leave us free and we understand nothing."

In reality, Nimes is just over 800 kilometres (500 miles) from Calais.

At night -- as they have done since reaching Calais two months ago -- Yussuf and his companions, aged 13 and 16, are back dodging police patrols to try to jump on a truck bound for the British El Dorado.

"Every night we try, but police big big problem," said Yussuf, looking frail and drawn from the nights sleeping rough.

Immigration Minister Eric Besson ordered the razing of the "jungle," used as a base by up to 700 migrants in June, after Calais officials complained it had become a crime magnet and a health hazard.

Besson says the raid was a blow to smuggling networks but rights activists denounced it as a media stunt that would drive migrants further underground.

On the Calais quays, a newly arrived Iraqi couple and their three-year-old son waited Monday with a hundred other Afghans, Iraqis or Eritreans outside a daily soup kitchen run by a local aid group.

"They are coming back little by little," said Francoise Peenaert of the Belle Etoile charity.

"But they are afraid. Now they are sleeping here and there, where ever they can," said the 61-year-old aid worker, handing out tarpaulins along with food to the destitute migrants.

At the local Catholic shelter, 40 migrants, most of them Afghans, used the free showers on Monday.

"It's around the same number as before they razed the Pashtun camp," said Catholic social worker Maurice Collier.

For Charles Framezelle of the C-Sur coalition of aid groups, the raid's main effect was to fray the nerves of the migrant population, some of whom hurled stones at a French television crew Monday.

Young migrants detained. Photo by Martin Bureau/ AFP

"Since Thursday, there has been incredible aggressivity in Calais. The migrants are all very tense," said the activist, who believes many of those who have returned are people-smugglers.

Britain, which last year stopped 28,000 migrants trying to cross the 35 kilometres (22 miles) that separate it from France, has hailed the crackdown and Besson insisted Monday it had been a "success."

"We achieved our goal, which was to destroy an insanitary camp and a hub for illegal smuggling to Britain," said the minister, announcing two more raids on migrants squats this week.

But Jack Lang, the Socialist lawmaker for the Pas-de-Calais region, slammed it as a failure.

"Anyone with a drop of common sense could predict that this dismantling would do nothing to solve the problem, and that inevitably the migrants would be back," he told AFP.

Rather than rounding up migrants, both the UN refugee agency and the EU's justice commissioner say the priority should be to offer full and fair asylum rights to migrants across the European Union.

Christine Bertrand-Nielsen/ AFP/ Expatica