Known as the Mule women of Melilla, hundreds of women carry heavy bales of goods across the border between the Spanish enclave of Melilla and Morocco every day. The law states that anything that can be carried by hand across the border is classified as luggage and is therefore duty free.

mule women of Melilla
A Moroccan woman carries a large bale of goods on her back across the border from Spain into Morocco David Ramos/Getty Images

Canny merchants employ women to carry their goods from Spain into Morocco, meaning they don't have to pay import taxes.

The bales, full of clothes, bolts of fabric, toiletries and household items, can weigh up to 80kg. The women earn about three or four euros per trip.

It is estimated that about 8,000 Moroccans, mostly women, are employed as "porteadoras". Many of them are widows, divorcees and single mothers struggling to feed their families, but now they face competition from unemployed Moroccan men.

This back-breaking work is lucrative – not to the women, but to Moroccan traders. It is thought that the goods carried across every year may be worth between 500 million and 1.4 billion euros.