BEIRUT — The Syrian military and allied fighters, backed by Russian airstrikes, on Friday pushed ahead with a major offensive in the north of the country, capturing another village and moving a step closer to encircling contested Aleppo, Syria’s largest city.

The offensive near the Turkish border, which began earlier this week, has sent tens of thousands of residents fleeing. Turkey has said about 10,000 Syrians have amassed on the Syrian side of the Turkish border and that about 70,000 more were on their way.

Meanwhile, there was mounting Western criticism of Russia’s military support for its ally, Syrian President Bashar Assad.

Russian airstrikes in Syria that mainly target opposition forces are “undermining efforts to find a political solution to the conflict,” NATO Secretary-General Jens Stoltenberg said Friday.

Russian air force activity in Syria has also led to increased violations of Turkish airspace, Stoltenberg said in Amsterdam, on the sidelines of a meeting of EU defense ministers. “This creates risks, heightened tensions and is of course a challenge for NATO because they’re violations of NATO’s airspace,” he said.

The Syrian government offensive comes at a time when hopes for a peace deal are increasingly dim, amid signs of possible further foreign military intervention.

Earlier this week, a U.N.-led attempt to launch indirect talks between a government delegation and opposition representatives in Geneva was adjourned after several days of acrimonious bickering.

At the same time, the Russian military said Thursday it had “reasonable grounds” to suspect that Turkey is making intensive preparations for a military invasion of neighboring Syria, while a Saudi military spokesman said the kingdom is ready, in principle, to send ground troops to Syria to fight Islamic State group extremists.