ASHGABAT -- Turkmen authorities have launched a campaign to register army reservists -- nearly all men under 50 -- amid concerns about militants in neighboring Afghanistan, according to a Defense Ministry source and accounts by citizens.

The Defense Ministry source told RFE/RL on January 14 that all conscription commissions across the Central Asian country had been instructed to register males younger than 50 and assess whether they are capable of taking part in military operations.

"It is linked to the tense situation along the border" with Afghanistan, said the source, who was not authorized to speak about the issue publicly and spoke on condition of anonymity.

An RFE/RL correspondent in the capital, Ashgabat, said that men under 50 had been summoned to local conscription commissions for medical examinations in recent weeks.

There has been no official announcement and Turkmen authorities have declined to comment.

Many Afghan districts bordering Turkmenistan are at least partially controlled by militants, mainly the Taliban, rather than by the internationally-backed Afghan government.

In December, a senior Russian military official said that the Russian Defense Ministry had resumed cooperation and joint training with Turkmen armed forces for the first time since the collapse of the Soviet Union in 1991.

Turkmenistan says it is neutral and has been reluctant to join international military and security groups since the Soviet collapse.

The head of the Collective Security Treaty Organization (CSTO) -- which includes Russia and several other former Soviet republics but not Turkmenistan -- said there was a danger of a "powerful extremist group" appearing along Afghanistan's borders with Turkmenistan and Tajikistan.

In January 2016, Russian Foreign Minister Sergei Lavrov said during a visit to Ashgabat that Russia was ready to help Turkmenistan patrol its southern border with Afghanistan, but that Turkmenistan did not need such assistance at the time.