Report: Ex-Syrian President Assad Poisoned

Putin personally granted asylum to Assad along with members of his family and regime associates.

Assad, 60, has not been seen in public since arriving in Russia and is assumed to be kept under close guard by Russian secret services.

An earlier report after Assad had been in Russia less than one month said that he 'complained to his security about feeling unwell and having trouble breathing'.

However, this account was not confirmed.

The U.S. state department estimates that the former dictator's family is worth $2billion, with their wealth concealed in numerous accounts, shell companies, offshore tax havens and real estate portfolios.

He, his British wife and their three adult children left behind their Syrian palaces and began a new life in Moscow when Putin granted them asylum in December.

They likely drew on their family connections and extensive assets in Russia to keep up their comfortable lifestyle in exile.

The autocratic dynasty is thought to have bought up at least 20 Moscow apartments worth more than £30million in recent years, illustrating Russia's status as a safe haven for the clan.

Asma al-Assad, the London-born doctor's daughter who has been battling an aggressive form of leukaemia, is widely believed to have arrived in Moscow with her daughter and two sons days before her husband finally fled Syria.

Secret tunnels beneath an Assad family mansion were reportedly uncovered after rebels seized the capital Damascus, with the network serving as a possible escape route for the dictator and his allies.

Meanwhile reports suggested that al-Assad could have fled via Russia's Khmeimim airbase, with flight trackers reportedly showing a Russian plane taking off from near the north-eastern city of Latakia just hours before he was reported to be in Moscow.

The unopposed takeover of the Syrian capital after a lightning offensive by rebel groups brought to an end a 13-year civil war and six decades of the Assad family's autocratic rule.

It was deeply embarrassing for Putin, after Moscow pumped military and financial aid into his government and bombed Syria for years to help prop up the Assad regime.