Armenian separatist authorities in an Azerbaijani region have passed a bill to designate Russian as a second official language, highlighting Moscow's growing influence in the South Caucasus.

Late last year, Russia mediated a ceasefire that ended six weeks of fighting between Azerbaijani and Armenian forces for control of Nagorno-Karabakh, a breakaway region of Azerbaijan. Under the agreement, Moscow stationed some 2,000 peacekeepers in Karabakh to oversee the truce and Armenia ceded to Azerbaijan swathes of territory it had controlled for the past three decades.

Armenian is the official language in Karabakh. Separatist deputy Aram Harutyunyan told AFP that the bill, which was adopted by the legislature on Thursday, "is aimed at fostering cooperation with Russian peacekeepers" and is expected to be signed into law by Arayik Harutyunyan, the separatist leader.

Lawmakers "will next week submit to the president draft legislation to make Russian a second official language in Karabakh", he said on Friday. Azerbaijan criticised the initiative, with President Ilham Aliyev saying that his country could have only one official language -- Azerbaijani.

The ex-Soviet South Caucasus countries have been locked in a territorial dispute for decades over Karabakh, where new fighting erupted in September, claiming the lives of some 6,000 people. Moscow mediated a ceasefire just as Armenia's defeat became imminent.

The deployment of Russian peacekeepers -- who guarantee the separatist authorities' survival -- further strengthened Russia's influence in Armenia, where Moscow has a military base and patrols the country's border with Turkey.