Russia said it had heard of reports that Tajikistan and Afghanistan were sending troops to their common border and urged them to resolve any dispute in a mutually acceptable manner, RIA quoted the Russian foreign ministry as saying on Friday.
It was not immediately clear to which reports the ministry was referring.
Tajik President Emomali Rakhmon has refused to recognise the Taliban-appointed cabinet in Kabul.
U.S. Defense Secretary Lloyd Austin expressed concern on Wednesday for U.S.-trained Afghan pilots and other personnel being held in Tajikistan after fleeing across the border from Afghanistan last month as the Taliban took power.
In the war's final moments, the U.S.-backed Afghan Air Force personnel flew dozens of military aircraft across the Afghan border to Tajikistan and Uzbekistan and were detained there.
Russia operates a military base in Tajikistan. (This story corrects to add "the ministry" in second paragraph instead of "he")
(Reporting by Vladimir Soldatkin; Writing by Olzhas Auyezov; Editing by Nick Macfie)
