The former Liverpool defender moved to the Cyprus outfit on transfer deadline day after being deemed surplus to requirements at Championship side Fulham.
The Norwegian left-back, 33, won the Champions League with Liverpool in 2005 and was a runner-up when the Reds lost to AC Milan in Athens two years later.
“All focused in my first session with my new team Great teammates who takes care of a new guy really happy with my decision to join APOEL @apoelfcofficial #winners #happy #apoel #nicosia #nr6 #champions #league #cyprus #hard #work #starts #now”
On Monday, Riise admitted the challenge of testing himself at Champions League level convinced the defender to join Apoel from Fulham.
“The main reason for joining APOEL is because they offered me a new challenge,” Riise said.
“The fact they are playing Champions League football and competing for the top titles in Cyprus means they are fulfilling my ambitions as a footballer. It is a big challenge for me to once again play in a top European competition.
“APOEL have presented me with a chance to play in the Champions League again and that makes me really happy as it was something I was not expecting.”
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