A Syrian court has ordered that Syriatel, owned by prominent businessman Rami Makhlouf, be placed under judicial custody amid a high-profile dispute over arrears, according to a document posted on the court's Facebook page.

Makhlouf, the cousin of Syria's Bashar Assad and one of Syria's richest men, had his assets ordered seized over alleged back payments to the country's telecoms regulator which it put at 134 billion pounds, or around $77 million at the current exchange rate on the parallel market.

Once at the heart of Assad's inner circle, Makhlouf has called the asset seizure illegal and an attempt by the government to take the company from him. The unprecedented public tussle has uncovered a rare rift in Syria's ruling elite.

The decision to place Syriatel under judicial custody is to "guarantee the rights of the public treasury and the rights of the shareholders in the company" the administrative court wrote on Facebook.

Makhlouf has addressed the dispute in three video messages in which he has appealed to Assad himself to help save his firm. In his last appearance, Makhlouf said he had been told to quit as the head of Syriatel.

Last month, a court placed a temporary travel ban on Makhlouf pending settlement of the dispute.