The 32-year-old had his his contract cancelled on transfer deadline day.

Ledley, who helped Wales make the semi-finals of Euro 2016, played just four times after Frank Lampard took over as Derby manager in the summer.

"I have never been the kind of person who can sit and watch football and not be playing play week in, week out," Ledley said on Twitter.

"I made the decision to terminate my contract with the club prior to the transfer window closing to give myself the opportunity to move on somewhere in the world of football and continue my career."

Ledley, who previously had spells at Cardiff, Celtic and Crystal Palace, has won 77 caps for Wales since his debut in 2005.

As he left Derby, fellow Wales international Andy King arrived from Leicester City.