Armenian-backed separatists said on Wednesday one of their soldiers was killed in clashes with Azeri forces along the boundary with the breakaway Nagorno-Karabakh region.

Clashes over control of the region, which lies inside Azerbaijan but is controlled by ethnic Armenians, have stoked fears of a wider conflict breaking out in the South Caucasus, which is crisscrossed by oil and gas pipelines.

Nagorno-Karabakh’s self-declared defense ministry said Azeri forces had been violating ceasefire agreements since the morning.

The Azeri defense ministry said that their forces detected and destroyed some Armenian combat vehicles during a maneuver.

“The Armenian armed forces have been suffering losses, mainly mercenaries of Armenian origin,” the Azeri defense ministry said in a statement.

Five Azeri soldiers were killed in clashes with Armenian-backed separatists last week and both sides have been accusing each other of an attempted incursion.

Fighting between ethnic Azeris and Armenians first erupted in 1991 and a ceasefire was agreed in 1994. But Azerbaijan and Armenia have regularly traded accusations of violence around Nagorno-Karabakh and along the Azeri-Armenian border.

The ceasefire was broken last April when dozens were killed. Efforts to secure a permanent settlement of the Nagorno-Karabakh conflict have failed despite mediation led by France, Russia and the United States.

(Reporting by Hasmik Mkrtchyan; additional reporting and writing by Margarita Antidze; Editing by Jeremy Gaunt)