Λ¿èGAnd when saved were seen to be from the number 4204.
Three messages every five minutes is too much to bear, right? Tried calling Airtel customer care. I did not know what exactly to ask them, I said junk characters are seen on my phone like a flash message. They said they will disable flash messages for my number. But the messages kept appearing. Went upto supervisor on Friday and Saturday. Still no respite - supervisor said that they are logging the issue, expect a resolution time of 48 hours. But till Tuesday, no respite.
The messages would stop at night after 9.30 or 10 pm and would start again the next day after 9 or 10 am. So I was led to believe this was some sort of message being sent by Airtel. But then I was wrong.
Finally thought of google - googled flash messages on airtel htc wildfire and found that these could be due to cell broadcast messages. Then googled disable cell broadcast htc wildfire and found this link which says Settings -> Call -> Other Call Settings -> Cell broadcast. But on my phone, it was in Settings -> Call -> Cell broadcast and was already disabled. I enabled it and then disabled it. And that resolved the issue!