Turkey's biggest clubs lured established stars including Mauro Icardi, Hakim Ziyech and Wilfried Zaha to the Super Lig in the transfer window with a spending spree that leaves them slipping further into the red.

Many eyes have been on Saudi clubs' remarkable transfer outlays which have rivalled those of the top European sides, but Turkish teams have been signing big names under the radar.

Fenerbahce, Galatasaray, Besiktas and Trabzonspor, the four biggest Super Lig clubs, spent almost 120 million euros ($128 million) between them during the summer window, which ended on Friday evening in Turkey, while only receiving less than 80 million euros in fees.

"It was a fiercely contested transfer window," said Galatasaray Vice-President Erden Timur earlier in September.

Timur said Turkish clubs were forced to change tack due to inflated fees caused by the Saudi clubs' sudden emergence.

"The average price (for players) multiplied by two or even two and a half, so we had to change strategy," he added.

"We had a spending limit and had to turn to free agents."

Galatasaray has brought in several household names, with former Crystal Palace star Zaha joining on a free transfer, while Ziyech and Tanguy Ndombele have signed on loan deals from Chelsea and Tottenham respectively.

Argentine striker Icardi was snapped up from Paris Saint-Germain for just 10 million euros after a successful loan spell last season, as defender Davinson Sanchez was signed for 9.5 million euros from Spurs.

Fenerbahce signed Cengiz Under from Marseille and Brazil midfielder Fred from Manchester United.

Alex Oxlade-Chamberlain and Eric Bailly have arrived at Besiktas on free transfers from Liverpool and Manchester United respectively, while Trabzonspor took on Nicolas Pepe when his Arsenal deal ran out.

Reigning Turkish champions Galatasaray spent 30 million euros this summer, down on the 43 million of the same window last year.

However, the payment of high salaries -- more than 90 million euros for the coming season just for Gala and arch rivals Fenerbahce -- risks plunging debt-ridden clubs into financial crises.

According to economist Kerem Akbas, author of a book on Turkish football finances, the big four clubs had two billion euros of debt between them at the end of August.

"There were a lot of recruits who were at the end of their contracts, like Icardi, who were cheap... but the salaries of these players are much higher than the clubs' income," Turkish sports journalist Alp Ulagay told AFP.

Ulagay said TV rights have lost significant weight for clubs in Turkey due to the devaluation of the Turkish lira against the euro and US dollar.

Only European competitions could help Turkish clubs make back their cash, but Galatasaray will be the sole Super Lig team in this season's Champions League.

The economist Akbas believes trying to appease devoted football fans in the country pushes clubs into spending money they cannot afford.

"Some salaries are covered by the sponsors although UEFA does not favour this," said Akbas.

"Every transfer window, the teams are essentially managed by the fans via social media.

"The clubs are in a tight financial spot as a result of fan pressure and executives' quest for fame...

"The government permits it. Otherwise, with these financial statements, the clubs would have gone bankrupt long ago."

There is no sign of Turkish clubs slowing down in their attempts to sign famous players.

Outside of the big four teams, another familiar face returned to Turkey on deadline day, as former Manchester City and Inter Milan striker Mario Balotelli signed for a second spell with Adana Demirspor.