Slovenia has requested the European Union to send additional police forces to its border with Croatia in order to deal with thousands of migrants flowing into the country to make their way to Austria.

Close to 19,500 migrants have entered Slovenia due to Croatia sealing its borders since Friday alone, creating bottlenecks at the Balkan border crossings, which has forced migrants to search for new routes through the area, according to Reuters.

"We need fast assistance of the European Union," President Borut Pahor said at a news conference in Brussels after meeting European Council President Donald Tusk and EU chief executive Jean-Claude Juncker.

The Slovenian parliament passed a new legislation Wednesday that will give the army more power to control the border when there are no police present. More than 18,469 migrants arrived in Slovenia since Friday, and at least 5,092 crossing the border on Tuesday, authorities say. Slovenia has offered assistance in the form of refugee centres and shelter, according to BBC News.

However, opposition parties say that the government should follow Hungary and put up a fence on Slovenia's border with Croatia to prevent migrants from entering the country. The same opposition is faced by other countries facing the refugee crisis, such as Germany and Sweden. Germany's policies of welcoming Syrian migrants continues to cause political divisions.

The government of Slovenia said that it is increasing the capacity of its reception centers to 14,000 beds. Croatia has pressed Slovenia to accept 5,000 people per day, but the government wants to limit that number.

"It is delusional to expect a country of 2 million to (accomplish) what much larger countries haven't been able to," the government said in a statement.

"It is of utmost importance here, as in other parts of Europe, that reception conditions be adequate to the task," UNHCR spokesperson Melissa Fleming said in Geneva, USA Today reported. "Without this essential element, the relocation program ... is in serious peril and may fail."