Fixed. "netstat -nlp | grep 53" output was:
It means it was not binding to extenal IP. "listen-on { 127.0.0.1; };" in named.conf prevented it from working correctly.
Code:
tcp 0 0 127.0.0.1:53 0.0.0.0:* LISTEN 28489/named
udp 0 0 127.0.0.1:53 0.0.0.0:* 28489/named