A Lebanese security source said Saturday that Bashar al-Assad's uncle, Rifaat al-Assad, left the country via Beirut airport around a week ago, after rebels overthrew his nephew.
Rifaat al-Assad, 87, is accused by Swiss prosecutors of a long list of crimes, including ordering "murders, acts of torture, inhumane treatment and illegal detentions" while an officer in the Syrian army.
His part in the notorious February 1982 massacre in the western city of Hama, in which between 10,000 and 40,000 people were killed, earned him the nickname "the Butcher of Hama".
Rifaat al-Assad arrived in Lebanon overland and "departed from Beirut airport normally, as there is nothing from Interpol on him" the security source told AFP.
He was not wanted by Lebanon's General Security agency and there were no other documents requesting his arrest, the source added, requesting anonymity as they were not authorised to speak to the media.
The source said Rifaat al-Assad departed Lebanon around a week ago and "used a diplomatic passport", without naming his destination.
Bouthaina Shaaban, a former translator for deceased Syrian president Hafez al-Assad and long-time political adviser to his son Bashar al-Assad, was similarly able to pass through Beirut airport, the source said, also on a diplomatic passport.
A friend of Shaaban in Beirut previously told AFP that the Assad adviser fled to Lebanon on the night of December 7-8 and then travelled to Abu Dhabi.
Islamist-led rebels launched a lightning offensive last month and took the capital Damascus on December 8.
A former vice president Syria, Rifaat al-Assad went into exile in 1984 after a failed attempt to overthrow his brother Hafez al-Assad.
He then presented himself as an opponent of his nephew Bashar al-Assad, who succeeded his father in 2000, travelling to Switzerland and later France.
In 2021, he returned to Syria from France to escape a four-year prison sentence for money laundering and misappropriation of Syrian public funds.
Earlier this month, Swiss newspapers reported that the country's Federal Criminal Court was considering dropping a case charging him with alleged war crimes and crimes against humanity.
The tribunal said that the defendant in his 80s was suffering from ailments that prevented him from travelling and taking part in his trial, the papers reported.