At least 23 people including civilians and the military have been killed after Fighting has erupted between Armenia and Azerbaijan around the separatist region of Nagorno-Karabakh.

The worst clashes since 2016 have raised the spectre of a fresh war between long-standing rivals Azerbaijan and Armenia which have been locked for decades in a territorial dispute over the Armenia-backed breakaway enclave.

Armenian Prime Minister Nikol Pashinyan announced in a televised address that Azerbaijan's "authoritarian regime has once again declared war on the Armenian people."

"We are on the brink of a full-scale war in the South Caucasus, which might have unpredictable consequences," he added. "We are ready for this war."

The office of Azerbaijan's prosecutor general said an Azerbaijani family of five were killed as Armenian separatist forces shelled Azerbaijan's village of Gashalty.

Rebel authorities in Karabakh said 16 of its troops were killed and more than 100 wounded in the fighting, as well as two civilians, a child, and a woman.

Both sides have accused each other of starting the hostilities.

Ethnic Armenian separatists seized the Nagorny Karabakh region from Baku in a 1990s war that claimed 30,000 lives.

Talks to resolve one of the worst conflicts to emerge from the 1991 collapse of the Soviet Union have been largely stalled since a 1994 ceasefire agreement.

In July, heavy clashes along the two countries' shared border — hundreds of kilometers from Karabakh — claimed the lives of at least 17 soldiers from both sides.

Raising the stakes, Azerbaijan at the time threatened to strike Armenia's atomic power station if Yerevan attacked strategic facilities.

Source: Agencies