The streets of Mosul are alive with the sound of Syrian traders touting their wares. But the Islamic State group, which controls the Iraqi city, plans to start taxing the traveling salesmen.

On the border between Mosul and Iraqi Kurdistan: Mosul under extremist rule has closed itself to Iraq, and opened roads to Syria.

The city of Mosul had turned its back to the other Iraqi cities as of the day it fell under the control of Daash, but it had opened its arms for the neighboring Syrian cities with which it shares the same fate because Mosul as well as those cities are all parts of the so-called "Islamic state".

Certain streets in Mosul now ring with the cries of Syrian traders. Locals in the Wadi Hajar neighbourhood in the city, which has been under the control of the extremist group known as the Islamic State since last June, are used to traders and street vendors touring their streets in cars or with trolleys and using loudspeakers to advertise their goods.

Ever since the city was taken over by the Islamic State, or IS, group Mosul has been increasingly cut off from Iraq. Instead the roads to the Syrian territories that the IS group controls have opened up. And now traders like the 45-year-old Syrian who wished to be known as Abu Staif have become well-known regulars in Mosul.

As soon as local women who want to shop hear him calling, the heavily veiled ladies surround his old Hyundai like black-faced bees around honey. The car has a sign that says “Syria – Homs” on it and its filled with kitchen and cleaning utensils and products like detergents.

Selling goods like this – on the streets – was very popular in Iraq between 1991 and 2003, when the country under Saddam Hussein was heavily sanctioned. Now once again merchants have returned to trade on the streets although this time they are mostly Syrian, rather than Iraqi.

From the start the IS group was keen to facilitate the movement of people between Syria and Iraq; the borders were open – in the IS group's eyes, they were actually non-existent – and the easy traveling between the two countries was a sign that the IS group's “caliphate” actually existed and that its territories were unified.

The Syrian traders are coming for various reasons. Mosul, with an original population of close to 2 million, is a big potential market. And almost all of the private factories and government plants here have ceased operations because of shortages of electricity and fuel or because they were targets for air strikes by the international coalition fighting the IS group; the extremists had often stored ammunition and weapons in the factories or used them to manufacture more.

There is also a lot of demand for certain goods in scarce supply in Mosul. There are mobile fuel stations that roam the city selling gasoline, kerosene or cooking gas and signs on the road advertising the availability of Syrian fuel. The fuel is often dirty, home made by villagers in Syria using primitive refineries. This has been necessary in Syria since the armed conflict began there and its become a real business for many.

The distance dictates which kinds of goods are brought to Mosul – clothing, sweets, fabrics and food are popular among sellers on the street. And despite the travel costs, some Syrian products end up being cheaper than any made or sold in Mosul, a fact that has caused consternation among local businesspeople.

One of his customers in Mosul asks Abu Staif why he would bother to make the long journey from Syria; for example anyone travelling from Raqqa, the IS group's “capital” in Syria, needs to drive for more than eight hours, over almost 500 kilometres. Abu Staif answered that he could almost double his profits in Mosul. “And here I buy used products from Mosul housewives and return with them to Raqqa where I sell them again,” he explained. “I just want to make a living.”

Abu Staif explains that each of his journeys from Raqqa to Mosul will last about two weeks so he's fitted his car out with cooking facilities and all the things he needs for overnight stays; mostly he and his friends spend their nights in car parks in the west of the city.

Of course, not all of the Syrian travellers are like Abu Staif. Some have now rented actual storefronts in Mosul's commercial centres, places like Bab al-Saray and the Corniche markets. And bigger changes are coming. The IS group has decided to make the street vendors organise themselves more formally. Shortly all of the sellers trading day and night, from trucks and cars, will be expected to park and sell in a new market in the central commercial district. Locals say it's not just because this would make the streets more orderly but because the IS group plan to charge the Syrian merchants tax too.