Germany's largest mosque will for the first time broadcast the call to prayer on Friday after city authorities in Cologne gave the go-ahead for a pilot project, under strict limits.

Cologne's Central Mosque, an imposing building in the western city's Ehrenfeld district, will be allowed to send out a single call to prayer over loudspeakers for up to five minutes on Fridays, between noon and 3:00 pm. The volume must not exceed 60 decibels.

The agreement, part of a two-year pilot project, was to be formally be signed by Cologne officials on Thursday.

Mosques in several cities in Germany have long been authorised to broadcast the call to prayer, but Cologne city only approved it from last October.

In majority-Muslim countries, the muezzin calls the faithful to prayer five times a day.

Cologne mayor Henriette Reker said allowing the call to prayer was "a sign of respect" for the city's many Muslims.