On a hot afternoon in the northern Italian border town of Ventimiglia, a group of well-dressed French tourists is making its way towards air-conditioned buses that will take them back to their homes along the Côte d’Azur.

They’re returning from a day of shopping at Ventimiglia’s lively Friday market, a mecca on the town’s seafront for visitors flocking across the frontier to rummage through an irresistibly cheap selection of clothes, food and trinkets.

They pamper a pooch who also joined them for the trip, seemingly oblivious to the scene playing out a few footsteps away from the car park: hundreds of migrants, the majority from war-torn Sudan, camped out among bags of rubbish beneath an underpass along the banks of the Roia river.

They are part of a growing and increasingly desperate army of migrants who have risked the perils of the Mediterranean, heading north as they flee war and poverty in Africa and the Middle East in search of security in Europe.

Ventimiglia has been a perennial waiting room since 2011 for migrants hoping to cross the border – just like the market shoppers. The town is gearing up for the holiday season as well as anticipating a new increase in migrant arrivals as Italy grapples with a sudden summer surge on its southern shores.

Some of the estimated 300 people sleeping rough along the Roia had only landed in Sicily a few days earlier.

“Whenever there’s an increase in arrivals in the south we see an increase in the number of people here,” said Daniela Zitarosa, who works for Intersos, an Italian aid organisation. “The number sleeping outside fluctuates, but it is always very high.”

Much like the rest of Italy, Ventimiglia has been left alone to deal with a humanitarian crisis that is growing dramatically and that now threatens to undermine the fragile unity of the EU, which is appearing to ignore the problems faced by its members in the south.

Facebook Twitter Pinterest French tourists shop in the street market in Ventimiglia. Photograph: Alamy Stock Photo

There was a time when French police would judiciously patrol the border while on the prowl for shoppers unwittingly transporting counterfeit purchases from the market. But since early 2011, when the migration crisis began in earnest as the Arab spring turned north African societies upside down, they have made the passage impenetrable to those desperately trying to join relatives or seeking a better life in northern Europe.

The patrols were stepped up after 84 people were killed in a terror attack in Nice, the French Riviera city just 39km along the coast, last July.

It only takes a few minutes to crawl into France by train from Italy, with the railway track crossing above the migrant camp along the river beneath. But it’s enough time for officers to saunter through the packed carriages, handpicking anyone they think might be a migrant before escorting them off at the well-manicured seaside resort of Menton-Garavan, the first stop along a route that passes through the wealthy principality of Monaco before arriving in swanky Cannes, and sending them back to Italy.

Officers are just as diligent at the entrance of the tunnel pass and along the motorway that connects the two countries, as well as along the so-called “passage of death”, a mountain trail that was used by Italian Jews fleeing the dictator Benito Mussolini’s Fascist regime during the second world war. French police reportedly use drones and dogs to sniff out trespassers, many wearing just flip-flops, making the risky journey.

At least 12 migrants have died since last September while trying to slip across the border, either by being hit by vehicles along the motorway or falling to their death from the mountain path. Alfatehe Ahmed Bachire, a 17-year-old from Sudan, drowned in June while trying to retrieve a shoe washed away by a strong current as he tried to clean his only pair in the Roia river.

“We know that 12 people have died, but the number is probably higher, as there may be more who died in the mountains on the French side,” said Zitarosa.

Meanwhile, a man from Afghanistan attempted to kill himself earlier this year after being warned that if he attempted to cross the border again he would be sent back to his European starting point in Italy’s south as part of a containment initiative by the Ventimiglia authorities. Another migrant died after throwing himself into the path of a truck in what is believed to have been suicide.

All Enrico Ioculano, the mayor of Ventimiglia, can do as he laments the lack of solidarity from France and other EU states, is to contain the growing crisis in his town. The 32-year-old, from Italy’s ruling centre-left Democratic party, has endeavoured to manage the issue for the last five years. There have been several tense moments between the two countries: more than 100 people stormed police barriers at the border last August, clambering across rocks as they tried to reach Menton.

Often rebuked by their French counterparts for failing to stop the crossing attempts, Italian police used teargas on a group of around 400 people as they marched towards the border in June.

“There are always lots of words coming from France, from François Hollande before and now from Emmanuel Macron – we’ll see what he tries to do. But for now, there is a total lack of synergy in managing this situation,” said Ioculano.

The only gesture of kindness has come from Prince Albert of Monaco, who is funding an information point staffed by Red Cross volunteers, who also ferry migrants arriving at the train station by bus to a refugee “welcome centre” on the edges of the city. But pessimists might conclude that this is simply a ploy to keep migrants away from his wealthy city-state.

Some 450 people are currently living at the facility, also managed by the Red Cross. Those sleeping by the river, an area lacking any kind of sanitation, do so because they don’t want to be fingerprinted when registering at the centre, despite having already gone through the procedure upon landing in Italy under EU rules which stipulate that those applying for asylum must do so in their first country of arrival.

Facebook Twitter Pinterest A group of migrants play football at the Italian Red Cross camp in Ventimiglia. Photograph: Eric Gaillard/Reuters

“They can leave the centre whenever they want, but they are very scared about giving their fingerprints, they don’t trust it,” said Zitarosa.

A further 70 women and children are looked after by Saint Anthony of Padua church, located over the road from the riverside camp.

People trying to help migrants have fallen victim to France’s no-nonsense patrols: French farmer Cédric Herrou was given a suspended €3,000 fine in February for helping migrants to cross the border and sheltering them in his home in the mountain hamlet of Breil-sur-Roya.

Ventimiglia is also taking a tougher stance: anyone caught giving food to migrants will be fined around €200 under a ban implemented by Ioculano last year. “I did this because it makes no sense if we have a Red Cross centre which provides food,” he said. “Nobody goes hungry. But I considered people giving food out on the street to be dangerous from a health and safety point of view.”

Down by the river, weary migrants while away the time in between border crossing attempts playing cards or sleeping. Some have tried to make the journey up to 20 times in one week, Zitarosa said.

Abdou Yahou, an 18-year-old from Sudan who arrived in Ventimiglia –dubbed Italy’s “mini-Calais” for being a migration bottleneck – a couple of weeks ago, fails to understand why a continent championing free movement won’t let him pass into France. Still, he’s happy to be safe.

“In my country there is war, at least in Europe there is liberty, maybe I will have that too one day,” he said. Alessandro Verona, a doctor with Intersos, visits the camp each day to check for illness and injury, the majority sustained from the crossing attempts or from trampling over broken glass. There are also many cases of bronchitis and occasional incidents of pneumonia.

But the most worrying symptom of the eternal wait is the mental anguish.

“For many, Libya was their passage through hell,” he said. “The stories I have heard from there are horrific. But now they look towards a passage that used to be a safe one for Italian Jews and all they can do is wait. They are stranded at a border between two of the founding fathers of the EU, both of which subscribe to the human rights’ convention.

“Ventimiglia is a contradiction about whatever we say in Europe about defending human rights.”