Thanks for your help. As suggested I started OpenNTPD in the foreground.
When using 'servers europe.pool.ntp.org' the following is echoed:
# ntpd -d -f /etc/ntpd.conf
listening on 192.168.0.1
ntp engine ready
reply from 213.239.193.168: offset 0.054319 delay 0.030604, next query 5s
reply from 213.84.46.114: offset 0.067833 delay 0.031135, next query 5s
reply from 213.84.14.16: offset 0.056339 delay 0.032713, next query 5s
reply from 80.253.108.112: offset 0.060374 delay 0.041055, next query 5s
reply from 193.120.10.3: offset 0.057984 delay 0.048810, next query 5s
reply from 62.206.102.82: offset 0.062085 delay 0.053013, next query 5s
reply from 81.31.113.153: offset 0.059202 delay 0.057052, next query 5s
reply from 212.41.248.75: offset 0.056436 delay 0.058490, next query 5s
reply from 81.221.24.146: offset 0.054919 delay 0.062901, next query 5s
reply from 195.197.174.39: offset 0.058256 delay 0.071470, next query 5s
reply from 62.101.81.203: offset 0.063421 delay 0.081010, next query 5s
reply from 81.56.228.174: offset 0.127634 delay 0.100761, next query 5s
reply from 130.206.130.95: offset 0.086618 delay 0.139101, next query 5s
If I understand correctly the time between queries is 5s. Unfortunately
after 30 minutes nothing happens and this is the only result. At the end
ntpd has to be forcibly killed.