ATHENS — The Greek police raided a site near downtown Athens on Friday that would be the capital’s first state-sponsored mosque, arresting 15 members of nationalist groups that had been occupying the premises in protest.

Athens is the only European Union capital without an official place of worship for Muslims, and although plans for the mosque predate the arrival of a huge of influx of migrants, many of whom are from Syria and Iraq, its construction has been caught up in the polarizing debate over how to handle the recent arrivals.

Nationalist groups have complained that the increase in Muslims threatens traditional Greek values, while the leftist-led government and Mayor Giorgos Kaminis, of Athens, have insisted that the creation of the mosque is an obligation for Greece as a European Union member state.

The protesters, who will face charges of disturbing the peace and have described themselves as patriots, moved to the plot of land in July to oppose the plans to construct the mosque, which was formally approved by Parliament in the summer after years of delays caused by protests and legal appeals. The project, budgeted at 887 million euros, or about $985 million, will be paid for by the Greek state.