tar archiving using shell script shows permission denied

Question

I am trying to auto-archive multiple logs file in a different directory. I've succeeded to archive every file but every time I executed the script it gives me a message like this:

./mainlog.sh: line 17: /opt/cafex/FAS-2.5.21/domain/log/alert.log: Permission denied

Here's some information about the script itself:

1. The script is located in (/root/) and already have (chmod +x permission)
2. The line that's giving me the message is this:

domain_log= $(sudo tar -cPzvf domain_log_$DATE.tar.gz /opt/cafex/FAS-2.5.21/domain/log/* --transform='s:/opt/cafex/FAS-2.5.21/domain/log/::g') 

I tried to do this:

domain_log= $(sudo tar -C /opt/cafex/FAS-2.5.21/domain -cPzvf domain_log_$DATE.tar.gz /opt/cafex/FAS-2.5.21/domain/log/*)

But the result remains the same (permission denied)

Does anyone have similar experience like me?