The Polish army said it had detained a group of about 100 migrants who crossed the Belarus border during the night, accusing Belarusian forces of leading the operation.

The incident came as Belarus, which has said it wants to defuse the crisis, prepared a first repatriation flight for migrants to Iraq that will have between 200 and 300 people on board.

Thousands of migrants, mainly from the Middle East, are camped out or staying close to the Poland-Belarus border in dire conditions aiming to cross into the European Union, in a crisis that began over the summer.

The EU says Belarus engineered the crisis in retaliation for sanctions on the ex-Soviet country. Minsk and its main ally Russia have rejected the charges and have criticized the EU for not taking in the migrants seeking to cross over.

In the latest border incident, the Polish defense ministry said that Belarusian forces had first carried out reconnaissance and “most likely” damaged the barbed wire fence along the border.