In the last week, it says more than 44,000 people crossed into Croatian territory.
Batch after batch are being brought by bus to the Opatovac transit camp, having crossed the border from Serbia.
It is baby Yara`s first birthday today. She fled war in Syria and is now crossing into Croatia #refugeecrisis pic.twitter.com/jTXvlSvjiK
— MSF Sea (@MSF_Sea) September 22, 2015
The asylum seekers are hoping to move on as quickly as possible to Austria, Germany and other countries.
Fleeing war and misery in the Middle East and Africa, they are crossing through Croatia after being blocked from entering Hungary by its metal fence.
A long queue of lorries heading into Croatia from Serbia also remains blocked.
Croatia has eased a cargo blockade, imposed in retaliation for Serbia directing the migrant flow across their joint border.
But Serbia has vowed political, legal and economic consequences unless the blockade is fully lifted by midnight, in a deepening dispute between the ex-Yugoslav republics over the refugee crisis.
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