World Uighur Congress (WUC) vice-president Ümit Hamit was detained by Hungarian police on suspicion of terrorism and expelled from Hungary last Thursday.
In addition, police and disaster response authorities prevented the meeting of the WUC and young Hungarians from four countries, arranged by the World Federation of Hungarians (MVSZ).
Hamit, a German citizen, told Radio Free Asia on Monday that China could be behind the incident.
In a video posted on the internet, MVSZ president Miklós Patrubány said police checked the papers of all delegates at the Hotel Attila where the visiting Uighurs were staying. Shortly afterwards, disaster response authorities closed the hotel down, saying it did not comply with fire regulations.
The MVSZ then offered the use of its headquarters on Downtown Semmelweis utca for the meeting.
Police went to the MVSZ headquarters 30 minutes before the scheduled meeting of Hungarian and Uighur youth and closed it, saying there had been a bomb threat. Disaster authorities then turned up at the building and said it had to be closed immediately.
Hamit was detained and questioned by Hungarian police for nearly 12 hours before he was expelled to Germany, where the WUC headquarters is located. Hamit said he was expelled without being shown any evidence.
National Police said Monday afternoon that Hamit is banned from entering Hungary.