Police in Slovenia say they have found 20 migrants from Pakistan in a van that crashed after entering the country illegally from Croatia.

They say a patrol chased the van, which then swerved off the road due to high-speed early on Wednesday. Several people have been hospitalised, one with serious injuries.

Police say the van had Austrian license plates and a Ukrainian driver who tried to escape by a crossing a river but stopped after a police warning.

The incident illustrates dangers migrants face as they try to cross borders illegally in an attempt to reach wealthy European nations. Several thousand have been stuck in Serbia waiting for a chance to move on.

The United Nation's International Organisation for Migration (IOM) recently estimated that the number of migrants and refugees travelling from Pakistan along the Central and Eastern Mediterranean routes for asylum and jobs in parts of Eastern Europe has been increasing since 2016.

Majority of such people are from Punjab followed by Khyber Pakhtunkhwa, Balochistan and the Federal Capital Territory (FCT), the IOM said.

Hundreds of thousands of migrants including Syrians, Iraqis, Pakistanis and Afghans have entered Europe in recent years.

At the height of the refugee crisis in 2015, over a million migrants arrived in Europe by sea, though the numbers have declined since a 2016 deal between Turkey and the European Union.