Assad, who last visited Russia in 2008, used the surprise visit yesterday evening to thank Putin for launching a campaign of air strikes in Syria last month, with the two leaders agreeing that military operations must be followed by political steps.
Putin pledged to continue to support Damascus militarily, while calling for a political solution involving all groups to try to end the war, the Kremlin said as it announced the visit today.
Assad told Putin the Russian air bombardments launched on September 30 - which have prompted an outcry in the West - had helped stop the spread of "terrorism" in his country, the Kremlin said.
The strikes are reported to have killed 370 people so far, a third of them civilians, according to a monitoring group.
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Russia insists the campaign is intended to target the extremist Islamic State group and others it describes as "terrorists".
Putin's spokesman Dmitry Peskov described Assad's lightning trip as a "working visit" at the invitation of the Kremlin, and by today morning, Assad was back in Damascus, the Syrian presidency told AFP.
It appears the Kremlin waited for the Syrian leader to return home before announcing the visit.
Peskov declined to say whether the "lengthy" talks, which also saw the two leaders and their entourages dine together, brought any firm results nor whether Assad's fate had been discussed.
Since then, more than 250,000 people have been killed and millions forced from their homes, sparking a mass migration of refugees that has raised tensions in Europe.
"We are ready to make our contribution not only during armed hostilities in the fight against terrorism but also during a political process," Putin said.
Assad also stressed the importance of "further political steps," according to the Kremlin statement.
"I need to say that the political steps which Russia has taken since the start of the crisis prevented the events in Syria from developing along a more tragic scenario," he said.