In general no, but it can depend. Some countries blur the line between police and military, that's when it can get foggy. If a country has a strictly civilian police force that does not take part in combat or training operations with the military, they are typically not valid targets. Just like any other armed civilian not taking part in combat is not a valid target.

During a total war any reasonable military will prioritise destroying their enemies capacity to wage war. That typically includes prioritising munition spending on military targets.

Bombing a civilian city centre can be demoralising, but history shows that it primarily serves to harden your enemies resolve, because you are explicitly showing that you are willing to harm the civilian friends and families of those fighting or otherwise supporting the war effort.

The bombing of Hiroshima/Nagasaki is a prominent counter-example of this though, where the weapons used were so completely terrifying that they helped convince Japanese leadership that their entire nation could be wiped out if they didn't capitulate. Still: there are strong arguments to suggest Japan would have capitulated anyway. Note that even though other bombing campaigns killed more people than the nukes, they didn't cause a capitulation.