Riga municipal police said Thursday that the Latvian Islamic Cultural Center had violated the law by celebrating a religious festival without the correct municipal paperwork.
Now a court will decide whether to punish the Muslim organization with a fine of up to €2,900.
Police received a tip-off from a concerned neighbor that a group of men was meeting in the courtyard of an apartment block at 104 Brivibas street.
Rushing to the scene, police found a prayer meeting in progress which was broken up on the basis that it was illegal because the gathering had not been cleared in advance with Riga City Council.
"We discovered that these people had taken actions in violation of public statutes on organization of public entertainments and festive events," Riga Municipal Police Bureau Chief Edgars Rudzītis said, explaining that gathering a large number of people together without permits presented a potential safety hazard.
Neighbors expressed their disgust at the thought Muslims could be praying nearby.
"Something like this - it's ludicrous! It's not for us, not for Latvia!" said neighbor Eriks Nore.
"I understand that they are founding another mosque. So we hope we will be rid of these neighbors!" said Mara Senberga.
Islamic Center press secretary Roberts Klimovics said the Brivibas street courtyard was being used only while a purpose-built mosque on Avotu street was being completed and that the event was held outside because apartments were too small to accommodate the large number of Muslims wishing to attend prayers.
A photograph of the assembly in question showed around 30 men kneeling and praying in the large courtyard.
Klimovics said the police approach was heavy handed.
"Throughout the world it is normal - people can pray where they please," said Klimovičs.
Karim, who arrived from Morocco and Latvian living here for five years, said that he understood the police concern but was disappointed that one of the major days in the Muslim religious calendar had been spoiled.
Police said the matter would be referred to the courts.