The U.S. military is setting up a base near northeastern Syrian town of Qamishli off Turkish border — an area controlled by the regime of Syrian President Bashar Assad, the Times UK reported Saturday. This comes a day after a Britain-based monitor suggested that Russia may want to rebuild an airport at Qamishli as a Russian base after Moscow sent several engineers to strengthen the runway and increase the capacity of the airport.

Local activists told the Times that U.S. forces were creating the base at a former agricultural airfield, about 31 miles from Qamishli and a few miles from the Iraqi and Turkish borders. Syrian Kurdish rebels control the area, according the Times report cited by the Australian.

Syrian activist Abu Jad Haskawi from nearby town Hasakah told the publication that American forces were reconstructing the airfield and using one airstrip for its helicopters and a command center. On Wednesday, U.S. officials confirmed that a small number of special forces soldiers were deployed, but did not disclose details about the activity in the region.

“Because of the special nature of these forces, it’s very important that we do not discuss specifically where they’re located,” Col. Steve Warren, an army spokesman in Baghdad, said.

U.S. intelligence sources told the Times that Russia appeared to be exploring the area for possible future fortification. The sources added that Russians seemed to have chosen the location to increase defenses against any possible action along the Syrian border by the Turkish military, which could include a move against the Kurds.

The U.K.-based Syrian Observatory for Human Rights reported Friday that Russian experts had “arrived to explore” the Qamishli airport’s “readiness and to check what is needed to develop and use it” near the Turkish border. The report added that Russian warplanes were expected to use the airport in the “coming days and weeks.” Qamishli is located south of the Turkish border town of Nusaybin.

The monitor’s report prompted Turkish President Recep Tayyip Erdoğan to express concern over Russian activity in the area. "We have said this from the beginning: we won't tolerate such formations [in northern Syria] along the area stretching from the Iraqi border up to the Mediterranean," Erdoğan said Friday, according to Agence France-Presse.

Russia, a supporter of Assad, launched airstrikes against the Islamic State group, also known as ISIS, in September 2015. But, Western governments have accused Russia of targeting Syrian rebels instead of the extremist group. On the other hand, Turkey is the key supporter of the Syrian opposition leading to tensions between Moscow and Ankara.

The two country’s relations have further strained after Turkish forces shot down a Russian warplane near the Syrian border in late November. Turkey said it downed the plane because Russia violated Ankara’s airspace — an allegation Moscow has consistently denied.

The Kremlin has accused Turkey of deliberately shooting down the Sukhoi Su-24M Fencer Jet on Nov. 24, 2015, and demanded an apology. However, Turkish Prime Minister Ahmet Davutoğlu said that his country would not apologize to Russia and cautioned that such incidents would remain a risk if Russia and NATO continue their air campaigns separately against ISIS in Syria.