Site hacked, new admin accounts being created

I’ve just cleaned a site following a recent hack, but noticed an additional admin account called ‘wp-admine’ with Administrator privileges.

I can delete this account but it immediately is recreated.

I have also tried deleting it from the user table using phpMyAdmin – but it is immediately recreated.

I have scanned the site with WordFence and it shows no malware. Please advise how to remove this hacker admin account and prevent it being re-added.

Thanks in advance.