It is allowed to perform Salāh in a church if there is some need as long as there are no images, idols or statues in them: Ibn Taymiyyah and Ibn Bāz
Shaikh Ibn Bāz (may Allah’s mercy be upon him) said: “Umar Ibn Al-Khattāb (radiyallāhu ‘anhu) allowed Salāh in a church if their was some need for the Muslims and soldiers [read on…]