Vladimir Putin decided to save his ally even as he concluded that there was nothing more he could do to support Bashar al-Assad's regime, Bloomberg reports.

al-Assad's fate was that of Russian agents, while his soldiers withdrew and returned to civilian clothes.

"However, Putin now wants to find out why the Russian intelligence service did not notice the growing threat to Assad's rule until it was too late," said a person close to the Kremlin.

According to three sources familiar with the situation, Russia convinced Assad that he would lose the fight against armed groups led by the former Al Qaiya branch HTS and offered him and his family safe passage if he left immediately.

Russian intelligence agents arranged the escape through their own airport in Syria, the two people said. The plane's transponder was turned off to avoid tracking, one of the two sources said.

Although the Kremlin wants to give the impression of coolness, Russian officials were surprised by the speed of events in Syria.

Russian state media say Assad is to blame for the defeat in Syria. While the Syrian army offered weak resistance, Russia concluded it could not protect the regime when rebels attacked the strategic city of Homs, one of the sources said.