Baku (AFP) — Armenia and Azerbaijan held peace talks on Monday, mediated by the United States, just hours after a fresh shootout along their troubled border in a conflict which has left hundreds dead in recent months.

Fierce fighting has broken out between Azerbaijan and its ethnic Armenian enclave of Nagorno-Karabakh, a new and dangerous eruption of a decades-old conflict.

Where and What is Nagorno-Karabakh?

It’s a mountainous, forested patch of land that sits inside the territory of ex-Soviet Azerbaijan and is recognised under international law as part of that country. But the ethnic Armenians who make up the vast majority of the estimated 150,000 population reject Azeri rule. They have been running their own affairs, with support from Armenia, since Azerbaijan’s troops were pushed out in a war in the 1990s. A ceasefire was agreed in 1994 but at least 200 people were killed in a violent flare-up in 2016. Nagorno-Karabakh survives almost totally on budget support from Armenia and donations from the worldwide Armenian diaspora.

Why has fighting broken out now?

Tensions between the two sides have been building over the summer, and spilled into direct clashes on Sunday. The timing is significant because the outside powers that have mediated in the past – namely Russia, France and the United States – are distracted by the COVID-19 pandemic, the upcoming U.S. presidential election and a list of world crises from Lebanon to Belarus. Lower-level clashes in July prompted only a muted international response. Turkey, which held large military exercises with Azerbaijan in July and August, has been even more conspicuous in its support compared with past crises. Turkish President Tayyip Erdogan said on Monday that Ankara would stand by Azerbaijan “with all its resources and heart”. He did not directly address whether Turkey is supplying the Azeri side with military experts, drones and warplanes, as Armenia has alleged and Azerbaijan has denied.

What are the Risks?

Past outbreaks of fighting have killed some 30,000 people since 1988. Already dozens have been killed and several hundred wounded in the latest flare-up. Olesya Vartanyan, an analyst with Crisis Group, said Monday witnessed an increase in deployment of heavy weaponry such as rockets and artillery, bringing a higher risk of civilian casualties that would make it harder to pull the two sides back from all-out war. That in turn could draw in other powers such as Turkey and Russia and destabilise the South Caucasus region, an important corridor for pipelines carrying oil and gas.

What could stop the fighting?

Several countries, including Russia and China, have called for a halt to hostilities but so far without any discernible impact. Russia potentially holds the key: it has a mutual defence pact with Armenia and a military base there, but also enjoys good relations with Azerbaijan and has no interest in the conflict spreading. If its diplomacy succeeded, Moscow could earn kudos for ending the fighting at a time when it is under intense criticism on other fronts, including over its backing for Belarus President Alexander Lukashenko after a disputed election and over the poisoning of Russian opposition politician Alexei Navalny in Siberia last month, which Germany says was carried out with a nerve agent. President Vladimir Putin spoke by phone to Armenian Prime Minister Nikol Pashinyan on Sunday but it is not yet clear if he has attempted to talk to Azerbaijan’s President Ilham Aliyev.

Nagorno-Karabakh is a mountainous and heavily-forested patch of land that sits inside the territory of ex-Soviet Azerbaijan.

Under international law, Nagorno-Karabakh is recognised as part of Azerbaijan. But the ethnic Armenians who make up the vast majority of the population reject Azeri rule. They have been running their own affairs, with support from Armenia, since Azerbaijan’s troops were pushed out in a war in the 1990s.

Long-standing ethnic tensions in the region between Christian Armenians and their mainly Muslim neighbours flared in Nagorno-Karabakh in the late 1980s. Hostilities this year have been the worst since 2016, when intense fighting killed dozens and threatened to escalate into all-out war.

Such a conflict could drag in the big regional powers, Russia and Turkey. Moscow has a defence alliance with Armenia, while Ankara backs its ethnic Turkic kin in Azerbaijan.

In the 1980s, the territory was within the borders of the then-Soviet republic of Azerbaijan, though most decisions were made in Moscow.

As the Soviet Union began to break up, it became apparent that Nagorno-Karabakh would come under the direct rule of the Azeri government. The ethnic Armenians did not accept that.

Sectarian conflict erupted, escalating into war in 1991 between Azerbaijan’s troops and Nagorno-Karabakh’s ethnic Armenian forces backed by Armenia. Thousands of people were killed and hundreds of thousands were displaced.

Authorities in Nagorno-Karabakh declared independence that year but it was not widely recognised internationally, leaving the ethnic Armenian administration there in a state of legal limbo and under blockade from Azerbaijan’s government.

By 1994, when an internationally brokered ceasefire was agreed, ethnic Armenians controlled almost all of Nagorno-Karabakh, plus some surrounding Azeri districts that gave them a buffer zone and land bridge connecting their region to Armenia.

Azerbaijan vowed to take back control over the territory, using military force if necessary.

International efforts over the years to find a lasting peace settlement, involving France, the United States and Russia as mediators, have failed to clinch a deal.