What is the ruling on praying in a mosque that contains a tomb (dharih), or what are known as mosques of the Awliya (saints), and must one re-perform the prayer if the worshipper was unaware of the tomb's presence?

We have previously clarified the ruling on building a mosque over a grave in earlier fatwas. Scholars have differed regarding the validity of prayer in a mosque that contains a grave. Some have maintained the validity of the prayer, though deeming it disliked (makruh), while others have declared it invalid. The safer approach is to adopt the view of invalidity.