I have an apartment which I gave to 3 students on rent. This month they vacated the apartment without paying the last month electricity bill. I have no written agreement but did police verification. So, what can I do now? Can I lodge a fraud complaint against them?
You will need to sue them for the money. You may decide that the cost and stress of doing so is not worth it, and just write off the cost.
In future you should require a deposit (if you don't already), and not return it until you have checked that the final utility bills have been paid. (I am assuming there was no deposit, or that you have returned it already; if not, you can pay the electricity company out of that deposit.)