Russia and its ex-Soviet ally Tajikistan have conducted “large-scale military drills” near the Central Asian country’s border with Afghanistan, reports Agence France-Presse (AFP), citing a Tajik military official.

AFP quotes Faridun Makhmadalizoda, a spokesman for Tajikistan’s defense ministry, as saying that the “drills involved about 50,000 Tajik troops and 2,000 Russian troops, including paratroopers flown in from Russia.”

“The maneuvers involve around 1,000 armored vehicles, artillery, and 32 combat and transport aircraft,” the spokesman told AFP, adding that they would continue until the end of the week.

According to AFP, the deployment of troops from Russia’s Central Military District to Tajikistan is unprecedented.

AFP notes:

This is the first time troops from Russia’s Central Military District have been involved in exercises in Tajikistan, highlighting Moscow’s growing unease over chaos in Afghanistan’s northern provinces.

The other Russian troops engaged in the exercises are from Moscow’s 201st military base in Tajikistan, the spokesman confirmed. Last year a contingent of 2,500 troops from the Collective Security Treaty Organization [CSTO], a military bloc led by Russia and including Armenia, Belarus, Kazakhstan, Kyrgyzstan and Tajikistan, also staged military exercises in the country.

In September 2015, a source close to the secretary general of the Russia-led CSTO was quoted by Kommersant as saying that the deployment of Russian forces to the Afghanistan-Tajikistan border was likely.

The source revealed that Russia was considering redeploying military troops to Tajikistan’s border with Afghanistan in response to the deteriorating security situation in Afghanistan that came less than a year after President Obama declared an end to the U.S. combat mission.

Citing the article from the Russian newspaper Kommersant, Khaama Press reported in September 2015:

The Russian forces may return once they receive a request from the government of Tajikistan… Russia is mulling the deployment of forces on Tajikistan’s border with Afghanistan amid fears that the security situation of Central Asia could deteriorate, specifically Tajikistan’s security.

AFP points out:

Afghanistan’s northern provinces have been rattled by militancy amid government infighting in Kabul and the drawdown of the US-led military presence. Skirmishes along the porous 1300-kilometer (810 mile) frontier Afghanistan shares with Tajikistan occur frequently.

Russia has a military base in Tajikistan and is reportedly concerned that instability there could intensify after the withdrawal of U.S.-led international troops from neighboring Afghanistan.