A ceasefire deal brokered last month to end six weeks of intense conflict between Armenia and Azerbaijan over breakaway enclave Nagorno-Karabakh has been breached for the first time.
The defence ministries of Armenia and Nagorno-Karabakh said the villages of Hin Tagher and Khtsaberd in the southern region of Hadrut were attacked by Azerbaijani forces.
The first breach was reportedly on Friday evening, with more skirmishes taking place on Saturday.
The Artsakh Defence Army, named after the Armenian term for the enclave, said three of its reserve soldiers were killed in Friday's skirmishes.
But Azerbaijan claimed the rival force provoked the encounter.
Russia, which is overseeing the peacekeeping operation in the region, confirmed the ceasefire had been breached.
"At twenty-three observation posts, Russian peacekeepers are monitoring the situation around the clock and control over the observance of the ceasefire," its Ministry of Defence told Tass news agency.
"On December 11, one case of violation of the ceasefire in the Hadrut region was recorded."
Armenia's Prime Minister, Nikol Pashinyan, and Azerbaijan's President, Ilham Aliyev, signed a deal on November 9 with Russian President Vladimir Putin, on a truce for Nagorno-Karabakh.
The deal included the return of occupied territories and the presence of Russian peacekeepers for up to five years.
It favoured Azerbaijan and led to victory parades in Baku and a month of protests in Yerevan.
Most of the Hadrut region was seized by Azerbaijan during bloody clashes, although some villages remained under the control of ethnic Armenians.
More than 5,000 people, including 144 civilians, died over the course of the short conflict.
That figure is expected to rise, with the operation to retrieve bodies still under way, hampered by icy and cold winter weather.
Nagorno-Karabakh is in Azerbaijan but is controlled by ethnic Armenians.