Incredible footage which purports to show Croatian police helping migrants illegally cross an unguarded border into Slovenia has been released by Slovene police, on a day when the country received more than 12,000 migrants.

The remarkable film, taken with a heat-camera fitted to a Slovenian police helicopter shows a heavily-laden passenger train pulling into the last stop before the Slovenian border before disgorging thousands of migrants.

Slovenian police claim the footage then shows Croatian officers corralling the migrants into a column which they then lead on a march to an unprotected section of border, before turning a blind eye as the group illegally crossed into the northern neighbour state.

In a statement released by Slovenian police, they say the train itself was unscheduled, indicating the service had been specially laid on for the purpose of clandestinely smuggling migrants out of the country without the knowledge of the country they were being dumped on.

Both Slovenia and Croatia find themselves on the migratory route through the Balkans heading north, and it seems Croatia has decided to help those migrants coming through the country to get out as quickly as possible.

Despite the clear and understandable concern shown by Slovenian police about the abuse of their national borders by their colleagues in Croatia, ultimately they were quite uninterested in protecting the border themselves. The force went on to explain their concern that the migrants were attempting to wade across the river Sotla to avoid detection, rather than crossing at an authorised and safer place. The statement explained:

“It is evident from the video that nobody [from Croatia] tried to stop them or direct them to a better crossing spot.

“The police helicopter used a searchlight to direct the people to a better spot. Migrants stopped getting into the water and gathered in a field, where they waited for transport. There were very small children among the wet and freezing people”.

Over 12,000 migrants arrived in Slovenia yesterday, a number that has completely overwhelmed police, the route having become more popular since neighbouring Hungary shut its borders last week. Slovenia has found dealing with the influx so difficult they have been forced to deploy a column of army armoured personnel vehicles to the border to quell tensions.

Watch: Migrants Arrive At Slovenian Border In Their Thousands