The Kremlin said Thursday that it "regretted" Armenia's decision to skip a summit of a Moscow-led security alliance, amid a souring of relations between the two ex-Soviet allies.

Neither Armenian Prime Minister Nikol Pashinyan nor his defense minister showed up to a meeting of the Collective Security Treaty Organization (CSTO) in Minsk on Thursday, which comes as Russia worries Yerevan could pull out of the alliance altogether.

When asked to comment on the absence of Armenia's delegation, the Kremlin said: "We can express regret in this regard."

"We hope that Armenia does not change the vector of its foreign policy and remains our ally… We will continue to talk to them," President Vladimir Putin's spokesman Dmitry Peskov told a state TV reporter.

Tensions between the two countries have run high since September, when Russian peacekeepers failed to intervene in Azerbaijan's lightning offensive against ethnic Armenians in Nagorno-Karabakh.

In a televised address after the conflict, Pashinyan denounced Armenia's traditional security alliance with Russia as "insufficient" and called on Yerevan to seek new partners.

Russia's Foreign Ministry said Wednesday it was "reckless" for Armenia to think it could rely on the West for security, and slammed Yerevan for "radically" changing its foreign policy.

Armenia's high-level snub marks yet another blow to bilateral relations, after Pashinyan shunned a summit attended by Russian President Vladimir Putin in October.