Austrian police say around 7,000 people gathered at the border after Slovenia transported many refugees by train.
Slovenia has started erecting a razor wire fence along parts of its border with Croatia amid heavy security to “direct the flow of migrants” into the country, the government has said.
Army trucks carrying wire fencing arrived in the border village of Veliki Obrez in southeastern Slovenia early on Wednesday to begin work on the barrier.
Slovenia does not plan to “significantly reduce” the flow of migrants into the country, Bostjan Sefic, state secretary at the interior ministry, said.
“The barriers do not have a purpose of preventing arrivals to Slovenia or significantly reducing them… Their purpose is to direct the flow of migrants to controlled entrance points,” Sefic told a news conference.
About 180,000 people, many fleeing war in Syria and Afghanistan, have entered Slovenia since mid-October, most of them heading north to Austria and then Germany.
Europe is facing a record influx of refugees and is deeply divided on how to act.
European Union leaders are due to meet in Malta for a special migration summit later on Wednesday to try to iron out their differences.
The main point of disagreement in the EU is over mandatory national quotas to share out the number of asylum seekers among the 28 member states.
Hungary, which closed its border to refugees in October, the Czech Republic, Poland, and Slovakia all strongly oppose the quotas.
Slovenia is facing more immediate and pressing logistical concerns. Prime Minister Miro Cerar said on Tuesday that the country, the smallest on the refugee route, does not have the resources to shelter large numbers over the harsh winter if Austria shut its border.
Slovenia’s border with Croatia will remain open, Cerar added, but the fence will prevent refugees from coming into the country outside the border crossing.
Soldiers guard fence
Slovenian soldiers also erected another 100 metres of wire fencing on an open field near the border village of Gibina in eastern Slovenia, a cameraman with the Reuters news agency there said.
The barriers do not have a purpose of preventing arrivals to Slovenia or significantly reducing them.
No migrants were present at either of the two places, but large numbers of soldiers and police were at both scenes, some guarding construction equipment, Reuters said.
Croatia on Wednesday said Slovenia’s move was unnecessary and a waste of money.
“It would be better if they built reception centres, similarly to what we did,” Croatian Interior Minister Ranko Ostojic told reporters.
“No wire can stop people to find their way and it is better to make their way organised.”
Slovenia said this week it was not going to build any long-term reception centres.
The UN refugee agency UNHCR said more than 3,000 people were waiting to enter a refugee camp at Presevo in southern Serbia, from where they will probably make their way to Croatia and then Slovenia.
Another 3,000 people were expected to enter Serbia on Wednesday, after 9,000 arrived a day earlier, a UNHCR field officer in Presevo said.
About 175 policemen from other EU states have come to Slovenia to bolster the local force. Another 100 are expected in the next two weeks.