MOSCOW, Russia - The Kremlin said on Monday it "categorically" disagreed with criticism of its peacekeeping forces in Nagorno-Karabakh, after Armenia accused Moscow of failing to intervene in Azerbaijan's lightning offensive last week.

The offensive, which saw Azerbaijan seize control of the region, deepened a growing rift between Moscow and Yerevan, which has increasingly pivoted its foreign policy away from its traditional security partner, Russia, in favour of the West.

"We categorically disagree with attempts to place responsibility on the Russian side or on the Russian peacekeepers, who are showing real heroism in carrying out their functions," Kremlin spokesman Dmitry Peskov said.

"Accusations that they are doing something wrong -- we will never accept such accusations," Peskov told reporters.

Armenia is a member of the Collective Security Treaty Organisation (CSTO), a Russian-dominated security alliance comprised of six post-Soviet states.

The group pledges to protect other members that come under attack but Moscow argued that Yerevan itself had recognised Nagorno-Karabakh as part of Azerbaijan, and refused to come to Armenia's aid.

Armenian Prime Minister Nikol Pashinyan told the nation in a televised address on Sunday that Armenia's current foreign security alliances were "ineffective" and "insufficient".

"The systems of external security in which Armenia is involved are ineffective when it comes to the protection of our security and Armenia's national interests," he said.