Reigning champion Rea finished outside the podium places, with the Northern Ireland rider crossing the line in fifth place.
Razgatlioglu has now opened a cushion at the top of the standings with three rounds of the championship remaining, and the Yamaha rider is in a strong position as he bids to become Turkey’s first World Superbike champion.
The 24-year-old was pushed all the way by Redding in race two, with the Ducati rider taking the lead with a few laps remaining.
Razgatlioglu, though, refused to settle for second place and fought back to retake the lead three laps from the finish.
Redding lost some ground after a slight mistake on the final lap and although he closed onto the rear of Razgatlioglu’s Yamaha again, he was unable to find a way past in a thrilling finish.
Spain’s Alvaro Bautista finished on the podium in third ahead of Razgatlioglu’s team-mate Andrea Locatelli, with six-time champion Rea next in fifth.
The Superpole race on Sunday was scrapped after Saturday’s racing was cancelled following the tragic death of teenager Dean Berta Vinales, who lost his life after a multi-rider crash in the World Supersport 300 race.
Portimao in Portugal hosts round 11 of the championship next weekend, bringing a frenetic run of three consecutive rounds to a close.
The penultimate round of the championship then takes place at San Juan in Argentina from October 15-17, with the final round at the new Mandalika circuit in Indonesia from November 19-21.