I had a similar issue recently and it was coming from the same provider/ASN.
After some hours, I installed the iptables xtables addon, got myself a fresh copy of the GeoIP database from Maxmind and temporarily blocked CN,VN,IN and RU to access my servers via iptables/xtables and immediately things were back to normal.
There’s always a small risk of overlocking when using access control based on GeoIP databases but I accepted that and it stabilized the situation quickly.