Istanbul - The head of a top European rights watchdog on Wednesday backed a "cleaning up" of Turkish institutions after a failed coup blamed on supporters of US-based preacher Fethullah Gulen.Despite growing concern over the post-coup crackdown, Council of Europe chief Thorbjorn Jagland said there had been insufficient understanding in Europe about the challenges faced by Turkey.His comments came as President Recep Tayyip Erdogan, in a rare apology, asked forgiveness for having an alliance with Gulen in the early years of his political career.Expressed alarmAlmost 26 000 suspects have now been rounded up after the coup, which Ankara blames on followers of Gulen who built up a presence in key institutions including the military. Gulen denies the accusations.Jagland's comments accepting the need for a crackdown contrasted with the tone of several EU officials who while condemning the coup have expressed alarm over the scope of the arrests. "I recognise that of course there is a need for taking on those who were behind this coup and also on this secret network," Jagland said after talks with Foreign Minister Mevlut Cavusoglu in Ankara."I would like to say there has been too little understanding from Europe over what challenges this has caused to the democratic and state institutions of Turkey," said Jagland, referring to Gulen's group. "We however have been informed about it for a very long time. So therefore of course we see a need for cleaning up all of this," added Jagland, one of the most senior European officials to visit Turkey in the wake of the botched July 15 putsch.State of emergencyAccording to Interior Minister Efkan Ala, 25 917 people have now been detained, 13 419 of whom have been remanded in custody over their roles in the coup.The CoE promotes democracy and the rule of law in Europe and its members include states who are not EU states like Turkey and also Russia.