* Militants take hostages in police HQ
* Unrest spreads in Sunni Muslim areas
* Syrian civil war deepens ethnic and religious faultlines (Adds Maliki speech, local vote result, security incidents)
By Suadad al-Salhy
BAGHDAD, April 25 (Reuters) - Nearly 50 people were killed in clashes on Thursday in the northern Iraqi city of Mosul, sources said, on the third day of the most ...