If this issue is on Safari as well, your device may be infected or may carry an app that causes this. I'd look through your apps for any abnormalities - you may also want to talk to Apple who can guide you better.

Thanks for the revert. I had posted this on Apple support forum wherein I got the following response:

Navigate to Settings/ tap Safari / select Clear History and website data

If it does not help your router may be hacked. Check the instructions on this page : http://www.thesafemac.com/how-to-manage-a-hacked-wireless-router/

So on applying the advice, I was able to figure out that my router is hacked.