A row has broken out between Croatia and Bosnia over the deportation of two Nigerian table tennis players who were wrongly kicked out of Croatia by police officers who allegedly mistook them for undocumented immigrants.

Abia Uchenna Alexandro and Eboh Kenneth Chinedu, students at the Federal University of Technology Owerri in Nigeria, arrived in Zagreb on 12 November, on their way to participate in the fifth World InterUniversities Championships, held this year in Pula, Croatia.

The 18-year-old table tennis players left Pula for Zagreb – the Croatian capital – after the tournament, and were supposed to fly back to Lagos on 18 November.

However, the night before their departure, while taking a walk in Zagreb they were stopped by two police officers who asked them for identification documents.

“We tried to explain who we were and that our documents were in the hostel, but they took us to a police station,” Chinedu told the Bosnian website Žurnal. “They paid no attention to what we were saying.”

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The officers allegedly mistook them for undocumented immigrants, put them in a van and transferred them to the border with Bosnia-Herzegovina where, that day, Croatian authorities had gathered together a group of migrants intercepted as they were attempting to cross the country. Police ordered the group to move through the woods and into Bosnia-Herzegovina.

Alexandro and Chinedu were eventually deported to Bosnia-Herzegovina and ended up in a camp in Velika Kladuša, where thousands of migrants are stuck in tents without water or heating with temperatures as low as -2C (28.4F).

“Those people are victims of illegal acts of the Croatian side,” Dragan Mektić, Bosnia-Herzegovina’s minister of security, told Al Jazeera.

“Respecting legal procedures, we now have to take them back to Croatia … it is obvious that they have Croatian visas, that they are in Bosnia-Herzegovina illegally. From their statements, it is obvious that Croatian police forcibly displaced them and we have to bring them back there.”

Žurnal reported: “Despite sophisticated equipment and the claim that they monitor every inch of the border, Croatian police cannot explain how the two Nigerians were transferred to Bosnia.

“When it comes to Schengen entry, the Croatian borders are impenetrable, according to the Croatian ministry of the interior. But when it comes to the illegal transfer of Nigerian students to Bosnia, everything is possible except that they were smuggled illegally by the police in Bosnia.”

A spokesperson for Croatia’s ministry of the interior said: “The claims stating that the Croatian police acts and judges individuals based on the colour of their skin are unacceptable and we firmly reject them.”

Police in Croatia have also raised doubts over the table tennis players’ intentions, suggesting that the men were lying. According to the police, another Nigerian who participated in the championship had attempted to cross the border with Slovenia from Croatia a few days before.

“Police officers have already witnessed cases of individuals who make an attempt to or even abuse their participation in sports competitions in Croatia to remain in the country,” or illegally continue their journey to other European countries, the Croatian police said.

The ministry of the interior has confirmed that Alexandro and Chinedu had regular visas and entered Croatia legally, but suggested that the students were making an attempt to remain and had checked out from the hostel before being stopped by the police.

The interior ministry in Zagreb said the men were stopped by the police on 18 November, the day they were due to depart, and not the day before as claimed.

However, the police’s version of events does not explain why the officers sent the students to Bosnia, knowing that they had entered the country with a flight to Zagreb and not from Bosnia.

Reached by the Guardian for further comment, the police did not respond.

Ranko Ostojic, a Croatian opposition leader who chairs the internal policy and national security committee and is a former minister of the interior, said the EU was shutting its eyes to the problem.

“I immediately asked the ministry of the interior to provide me with details regarding the two Nigerian students,” he told reporters in parliament.

“This case, of course, raises once again the question of what we have been saying all this time, and that is that the deterrence is happening in the depths of the territory, and that even people who come to sports competitions now run the risk of being thrown into a van and brought to Bosnia.”

According to Bosnian media, Alexandro and Chinedu have been moved to Sarajevo, as authorities work on an immediate solution to the case. However, the Bosnian ministry of security did not confirm the news.

The organisers of the World InterUniversities Championships have called for the pair to be returned safely to their own country.