Ruling on buying a mosque with an interest-based loan

We are a group of foreign Muslims living in Germany. We have a place which we rent for the daily prayers, Jumu’ah and Eid. But because there are so many people praying there – praise be to Allaah – the German government will no longer allow us to pray there, because the place is too small and is a place that is not suitable. Now we want to buy a big place outside the city, and the German authorities have agreed that we may buy it. The place costs 3.5 million deutschmarks, and we have only 1.5 million deutschmarks. Is it permissible for us to take out a loan from the bank to cover the outstanding amount and buy this place with ribaa (interest)? Is this considered to be a necessity? If we buy it with ribaa, is it permissible to pray in it until we have other places in the city to pray in? Please advise us, may Allaah reward you.