Lebanese sources said on Wednesday Russian forces have begun participating in military operations in Syria in support of government troops.
Stoltenberg joined other western leaders in calling for a political rather than military solution to the four-year-old multi-sided civil war, which has killed 250,000 people and driven half of Syria’s 23 million people from their homes.
“I am concerned about reports about increased Russian military presence in Syria,” Stoltenberg told reporters during a visit to Prague.
“That will not contribute to solving the conflict. “I think it is important to support all efforts to find a political solution to the conflict in Syria.” Officials in the United States, which is fighting an air war against the Islamist militant group Islamic State in Syria but also opposes Bashar Assad’s government, have said in recent days that they suspect Russia is reinforcing aid to Assad.
Moscow confirmed it had “experts” on the ground but declined to comment on the exact scale and scope of its military presence.
Germany’s foreign minister warned Russia against increased military intervention, saying a nuclear agreement with Iran and new U.N. initiatives offered a starting point for a political solution.
French Foreign Minister Laurent Fabius said reports of Russian troops would complicate efforts to find such a solution.
Speaking on the conflict between government forces and Russian-backed rebels in eastern Ukraine, Stoltenberg said an often violated ceasefire seemed to be more observed now than for a long time before, but the situation remained fragile.
Government and separatist representatives agreed in late August to strive to end all violations from last Tuesday.
President Petro Poroshenko said on Tuesday the country still faced the threat of a full-scale Russian military attack despite several days of relative calm.
(Reporting by Robert Muller; Writing by Jan Lopatka; Editing by Larry King)