Was offered a PhD position, I accepted it but no replies afterwards from the potential supervisors I gave an interview for a Phd position and I was offered the position within a day of the interview. I accepted the offer withing two days (before the deadline) and sent an email stating my acceptance of the offer to the supervisor who interviewed me. No acknowledgement was given  and thereafter I have not received any further emails from their side. I sent another email to follow up and ask if they received my first email, but still no replies. It is now been 2 weeks since they last emailed me. Should I keep waiting, or send another email or just move on and apply for other positions.

I tried all emails I could find to contact them. It is not an email delivery problem, since I corresponded with them using the same email many times before the interview took place and I am receiving emails from other people without any problem. 

Edit : Now I have another PhD offer and have a deadline to acfept and reject. Still no replies from the first offer. It is almost been a month now.

What would be the best way to go ahead in this situation? I don't want to be dishonest by accepting both offers and but I also don't want to lose both in case the first offer doesn't work out.
The first offer was not an official one. The email read ' We would like to offer you in the position.'
I don't think you have any reason to worry. Under the current strain and disruption of the pandemic people aren't able to do the things they would normally do. A couple of weeks isn't very long after a deadline as there are probably quite a few administrative tasks that seem to them to be more important to them than reassuring students. The professor in question might have additional issues preventing them from responding in a timely manner (or at all, if they are ill or caring for a family member). 

Assume that all is well. You've done what was required of you. 

Don't keep hammering, though, as it just makes their workload worse. 

On the other hand, you are due an acknowledgement that all is well. A once-a-week email is probably appropriate until you get confirmation. 

Note that normal phone numbers aren't being answered at some places. Buildings are locked and people are forbidden to enter, even to retrieve personal effects. 



You could, however, keep abreast of any news pertaining to that university by doing web searches. There is a lot of disruption and universities are planning how to finish out this year and finding ways to be flexible for next. Bad things are happening. They could continue to happen.