Story highlights Satellite images show expansion of a runway and possible U.S. activity

Russia could be making moves to establish an air base in northeastern Syria

Officials say the U.S. has seen some Russian military personnel in the area

Washington (CNN) Russia could be making moves to establish an air base in northeastern Syria on the border with Turkey, a development that could further complicate the overall situation in the region, two U.S. officials have told CNN.

The United States has seen a "limited" number of Russian military personnel, more akin to an exploratory party, looking at an airfield in Qamishli, Syria, possibly to determine how they might use the site, the officials said Thursday.

"We don't know what their intent is, but it is something we are watching closely," one official said, citing the already fraught relationship between Turkey and Russia after Turkey's shootdown last year of a Russian military jet that Ankara said had breached Turkish airspace.

The move was first reported by Fox News.

Relations between the two nations, already at a low point, could be exacerbated if Russia built up its presence along the border, officials say.

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