The Syrian government ordered the seizure of assets belonging to President Bashar Al-Assad's cousin Rami Makhlouf, one of Syria's richest men, as well as his wife and children, according to a government document reviewed by Reuters.
The document, stamped 19 May and signed by the Syrian finance minister, said the "precautionary seizure" aimed to guarantee payment of sums owed to the Syrian telecom regulatory authority.
Once at the heart of Al-Assad's inner circle, Makhlouf has quarrelled with the authorities over funds which the government says are owed by his mobile phone company Syriatel.
The unprecedented public tussle has uncovered a rare rift in the ruling elite.
Makhlouf has addressed the dispute in three online video messages in which he has appealed to Assad himself to help save his firm.
In his last message, released on Sunday, Makhlouf said he had been told to quit as the head of Syriatel.
The government says Syriatel owes 134 billion pounds (around $77 million) at the current exchange rate on the parallel market.
Makhlouf today posted a letter dated 18 May denying allegations by the Ministry of Telecoms that Syriatel had rejected payment of amounts it was required to pay in a dispute over its license.