Syria's Justice Ministry on Thursday announced a travel ban on Rami Makhlouf, a Syrian businessman and cousin of President Bashar Al Assad, over money it says he owes the state.
Mr Makhlouf, the head of Syria's largest mobile operator Syriatel, has been grappling with authorities over demands that the company pay $185 million (Dh679.5m).
Syria's telecommunications authority has threatened to take all necessary measures to recover the money, which it says Syriatel owes for maintaining its operating licence.
But Mr Makhlouf has called the claims undue and unjust.
On Thursday, the ministry published on its Facebook page a court order "temporarily banning the defendant from travelling abroad" until the case was resolved or outstanding payments were made to the authority.
The document, signed on May 20, said the ban was requested by the Telecoms Minister and the general manager of the authority in a lawsuit they filed against Mr Makhlouf.
"The court finds that it is likely the defendant is indebted in light of the documents presented," by the plaintiffs, the ministry said.
Mr Makhlouf, who also has stakes in electricity, oil and property, said on Tuesday that the telecoms authority was seizing his assets and those of his family.
He said he also received notice from the government that he would be "banned from working with the state for five years".
Mr Makhlouf, who had kept a low profile throughout Syria's nine-year war, responded with online attacks against Syrian authorities in recent weeks.
At the end of April and again in early May, he said that some people in government were out to get him and his company.
Analysts say this suggests a growing isolation from the centres of power, including Mr Al Assad.
Signs of a dispute emerged last summer when Syrian authorities seized Mr Makhlouf's Al Bustan charity and dissolved militias affiliated to him.
The Finance Ministry in December froze the assets of several businessmen over tax evasion and illicit enrichment, and the Syrian press said Mr Makhlouf, his wife and companies were among them.
In recent weeks, Syrian security services have detained several of his employees in a move he says is meant to intimidate him into stepping down from his businesses.
The Syrian Observatory for Human Rights said from Britain that dozens of employees from Al Bustan and Syriatel have been arrested since April.