Amnesty International said combatants in an escalating conflict between Armenia and Azerbaijan were using cluster bombs, and called for protection of civilians who are highly vulnerable to the indiscriminate destruction wrought by the weapons.

The rights organisation said footage "consistent with the use of cluster munitions" in the Nagorno-Karabakh capital Stepanakert had been released by the city's de-facto authorities at the weekend.

The warning comes after separatist forces in Karabakh -- an ethnic Armenian enclave that broke away from Azerbaijan in the 1990s -- reported firefights along the frontline, and said Stepanakert had again come under artillery fire.

In a statement Monday, Amnesty said its experts had traced the location of the footage to residential areas of Stepanakert, and identified Israeli-made M095 DPICM cluster munitions that, it said, "appear to have been fired by Azerbaijani forces".

Cluster munitions typically scatter submunitions over a wide area where they often fail to explode, posting a threat to civilians similar to that of anti-personnel landmines, Amnesty said.

A 10-year-old convention banning cluster bombs has been signed by more than 100 states, but not by Armenia or Azerbaijan.

After "corroborating the use of banned cluster bombs in the region", Amnesty said the protection of civilians had to become a priority.

"The use of cluster bombs in any circumstances is banned under international humanitarian law, so their use to attack civilian areas is particularly dangerous and will only lead to further deaths and injuries," Denis Krivosheev, Amnesty's acting head of Eastern Europe and Central Asia, said in the statement.

"Cluster bombs are inherently indiscriminate weapons, and their deployment in residential areas is absolutely appalling and unacceptable," he said.