Russia is stepping up its assistance to the embattled Syrian government in what appears to be an effort to boost President Bashar Assad’s beleaguered forces and to address the rise of Islamic extremist groups, the director of the CIA said Thursday.

The comments from John O. Brennan come a day after the Russian Foreign Ministry acknowledged having military advisers in Syria, but said they were part of a long-running military agreement between the two allies. Russia’s increasingly public role in Syria has been a new source of friction between Moscow and Washington.

“Russians have been very candid, not only that they have a presence  . . .  but also that there is some additional people and stuff finding its way into Syria,” Brennan told a Washington conference on intelligence and national security.

He said the Russians have trainers and advisers in Syria, and also noted the long-standing Russian naval facility in the port city of Tartus on Syria’s Mediterranean coast.

Brennan did not go into detail on what all Moscow has moved into Syria in recent weeks, but he said the maneuvering appears to have two goals: to protect the Syrian government, a Kremlin ally for decades, and to address concern about the simmering threat posed by the Islamic State and the al-Qaeda-affiliated Nusra Front that have emerged from Syria’s civil war.

Chechen fighters, in particular, play a very outsized role in many radical militant groups in Syria and to a lesser degree in Iraq, which is of considerable concern to Russia.

The CIA director said Moscow has expressed similar concerns as the U.S. about the growth of the Islamic State and the Nusra Front. Brennan added that he and other senior American officials have spoken to their Russian counterparts about the need to collaborate on the terrorism issue, but he also stressed that the U.S. does not share “in any way” Moscow’s support for Assad.

He did not elaborate on how the United States could work together with Russia against Islamic extremist groups in Syria.

Assad’s forces have suffered a series of losses across the country in recent months. In central Syria, the Islamic State captured the town of Palmyra, home to monumental ancient ruins dating back to Roman times, in May. Earlier this spring, an array of Syrian rebel groups working in tandem with the Nusra Front captured the northwestern city of Idlib and much of the surrounding countryside.

Brennan suggested that those losses might have spurred Russia to ratchet up its support for Assad’s forces.

“I don’t think anyone wants the collapse of the Syrian government, for there to be an implosion inside of Damascus,” he said. “But I think some of the setbacks that the Syrians have suffered have probably encouraged the Russians to move forward with stepping up some of their assistance.”