Supporters of Turkish President Recep Tayyip Erdoğan attend a rally on July 31, 2016 in Cologne | Oliver Berg/AFP via Getty Images German court bans Erdoğan from addressing Cologne rally Ankara questions decision to not allow president appear in live broadcast.

Germany's highest court upheld a ban on Recep Tayyip Erdoğan broadcasting a message to supporters at a rally in Cologne on Sunday, leading the Turkish president's spokesman to question the "real reason" behind the decision.

Thousands of Erdoğan's supporters attended the rally in the city in western Germany to express support for his policies following a failed attempt by a group within Turkey's military to overthrow the government on July 15.

According to an Associated Press report, Erdoğan's spokesman Ibrahim Kalin said Sunday that Turkey was "curious what the real reason is behind why German local courts and the Constitutional Court have prevented [Erdoğan's] message, and hope German officials will provide a satisfactory explanation."

Police in Cologne said Turkey's sports minister is expected to attend the rally, but authorities imposed the condition that no messages from speakers elsewhere, such as politicians in Turkey, could be shown on a video screen, Associated Press reported.

The German Constitutional Court decided late Saturday to uphold that policy.

It comes amid concerns in Germany and elsewhere in the EU over Erdoğan's harsh crackdown following the failed coup.

The president declared a state of emergency and purged the military, courts and the media of tens of thousands of employees on suspicion they had participated in the attempt to oust him.

Zafer Sirakaya, head of the Union of European Turkish Democrats that organized the Cologne rally, criticized the court ruling and said it was politically motivated.

"There is no acceptability to this ruling from a legal perspective. It is extremely clear that this is a political decision," Sirakaya told the Anadolu press agency.