The leaders of ex-Soviet states, led by Russian President Vladimir Putin, responded to growing instability in Afghanistan on Friday by agreeing to create a joint task force to defend their bloc's external borders if a crisis arises.
The move could mean that Russian troops, as part of collective forces, will be deployed to Afghanistan's borders as the U.S.-led coalition gradually withdraws from the country, leaving behind a power vacuum.
If Russian troops do move in, it would be a fresh sign of Putin's new military assertiveness, after his intervention in Syria.
The Kremlin says Russia wants to stop the spread of Islamist militancy, but Western governments also see it as Russia trying to re-assert itself as a global power.
The leaders of ex-Soviet grouping the Commonwealth of Independent States (CIS) met at the Burabai resort near the Kazakh capital, Astana.
They agreed on the creation of what is described in a summit document as a "grouping of border (forces) and other institutions from CIS member states designed to resolve crisis situations on the external borders".
There were no details on the composition of the force or on where it would be deployed.
But Sergei Lebedev, the CIS executive secretary, mentioned Tajikistan, which has a border with Afghanistan, as the possible location for the deployment of joint forces.
"Apart from Russia, there are collective forces aimed at supporting Tajikistan against those threats from the south," he told reporters. "Whether or not Russia is going to return there (to patrol the border) is a matter that will be resolved through bilateral agreements."
Russian border troops were responsible for security on the Tajik-Afghan border until 2005, when an agreement with the Tajik government lapsed and they pulled out.
Impoverished Tajikistan has the longest border with Afghanistan among the ex-Soviet nations and remains volatile since a 1992-97 civil war between its Moscow-backed secular government and Islamist guerrillas.
On the other side of the border, Taliban insurgents have made advances, including briefly taking over the city of Kunduz late last month.
It remained unclear whether the two other Central Asian nations which border Afghanistan, Uzbekistan and Turkmenistan, would also host the new joint task force.
Turkmenistan's foreign ministry said on Friday it had registered no incidents on its border with Afghanistan.
(Reporting by Denis Dyomkin; writing by Vladimir Soldatkin and Olzhas Auyezov; editing by Giles Elgood)