Armenian Prime Minister Nikol Pashinyan on Thursday questioned the role of Russian peacekeepers in the disputed region of Nagorno-Karabakh after a new flare-up left three soldiers dead.

Pashinyan's rare criticism of ally Moscow came after tensions escalated on Wednesday in the disputed mountainous region, which is mainly populated by ethnic Armenians.

The former Soviet republics of Armenia and Azerbaijan have fought two wars -- in the 1990s and in 2020 -- over Nagorno-Karabakh.

In the aftermath of the latest war, Armenia ceded swathes of territory it had controlled for decades.

Russia deployed some 2,000 peacekeepers to oversee the fragile truce but tensions persist despite the ceasefire agreement.

'Questions arise in Armenian society over the Russian peacekeeping operation in Nagorno-Karabakh,' Pashinyan told a government meeting.

He pointed to 'gross, prolonged violations of a ceasefire regime' and 'constant physical and psychological terror' of Karabakh residents in the presence of the peacekeepers.

Pashinyan said the role of the Russian peacekeeping mission must be 'clarified', adding that Armenia expected the contingent to prevent 'any attempt to violate the line of contact'.

The two sides accuse each other of violating the fragile truce.

On Wednesday, Baku said it had lost a soldier and the Karabakh army said two of its troops had been killed.

The Azeri defense ministry said Karabakh troops targeted its army positions in the district of Lachin, which is under the supervision of the Russian peacekeeping force.

The Azeri army later said it conducted an operation dubbed 'Revenge' in response and took control of several strategic positions.

On Friday, Russian President Vladimir Putin is hosting Turkish President Recep Tayyip Erdogan for talks in the Black Sea resort city of Sochi.

Turkey backed Azerbaijan in the 2020 war over Nagorno-Karabakh.