Moscow has held military exercises in Tajikistan and expanded the hardware at the base, its biggest in a foreign country, since the U.S. withdrawal of troops from Afghanistan and the Taliban’s lightning takeover.

Russia is worried about the potential for fallout in the wider region and the possibility of Islamist militants infiltrating Central Asia, which Moscow sees as its southern defensive buffer.

Tajikistan’s border with Afghanistan stretches for 1,344 km (835 miles), and much of it is mountainous and hard to police.

Interfax quoted Khanif Beglov, tank unit commander of Russia’s Central Military District, saying 30 modern tanks would be stationed at the base by the end of the year to replace older combat vehicles.