MADRID (Reuters) - Spain's High Court has annulled 91 million euros ($100 million) of fines imposed on four Spanish banks, including Santander and BBVA, for selling interest rate derivatives to customers above market rates.

The competition watchdog imposed the fines after it considered the lenders, which also included Caixabank and Sabadell, had fixed above market rates the price of derivatives that were used to hedge the interest rate risk associated with syndicated loans for project finance.

"The court considers that it has not been accredited that during the entire period under investigation from 2006 to 2016 there was a common plan between the sanctioned entities that justifies the legal classification of a single and continuous infringement", the court said in a statement.

The court upheld the appeals filed by Santander, BBVA Sabadell and Caixabank against the watchdog's rulings of Feb. 13, 2018.

The CNMC watchdog had imposed fines of 31.8 million euros on Caixabank, 23.9 million on Santander, 19.8 million on BBVA and 15.5 on Sabadell.

The High Court decision is not final and can be appealed.

CNMC declined to comment.

($1 = 0.9121 euros)

(Reporting by Jesús Aguado; Editing by Emma Pinedo and Mark Potter)