Thousands of Armenians flocked Saturday to a memorial of the World War I-era mass killings of their kin by Ottoman Turks, the bloodletting which US President Joe Biden is reportedly set to recognise as genocide.

Armenia lifted martial law on Wednesday, five months after the end of its brutal war with Azerbaijan over the Nagorno-Karabakh region.

Armenian leader Nikol Pashinyan accused the military of an attempted coup and urged supporters to take to the streets Thursday, after months of tensions over his handling of last year's war with Azerbaijan.

Armenian Prime Minister Nikol Pashinyan led Saturday a thousands-strong march in memory of those killed in clashes with Azerbaijan as the Caucasus country began three days of mourning amid persisting tensions.

Separatist officials in the breakaway region of Nagorno-Karabakh said Saturday that three fighters were wounded in a skirmish with Azerbaijani forces, undermining a recent peace deal brokered by Russia.

The defence ministry in the ethnically Armenian province said in a statement that Azerbaijani troops attacked Friday evening and that "three Armenian servicemen were injured during the ensuing gunfight". 

Armenian protesters on Tuesday blocked streets in the capital Yerevan, launching a "civil disobedience" campaign to force Prime Minister Nikol Pashinyan to quit over a controversial peace agreement with Azerbaijan.

Shouting "Armenia without Nikol" and "Traitor", opposition supporters blocked traffic across the capital and paralysed the city's subway. Police detained dozens of demonstrators.

Azerbaijan said Thursday that nearly 2,800 of its soldiers were killed in recent fighting over Nagorno-Karabakh, the first details it has released of military losses in weeks of clashes with Armenian forces.

Azerbaijani soldiers and military trucks rolled into the district of Kalbajar on Wednesday, reclaiming the second of three regions Armenia is handing back under a deal that ended weeks of fighting.

Armenian Prime Minister Nikol Pashinyan called Saturday for greater military cooperation with Russia, a day after Azerbaijani troops began moving into territory in Nagorno-Karabakh previously held by Armenian separatist forces.

Armenia on Saturday said that more than two thousand fighters were killed in six weeks of clashes with Azerbaijan over the disputed Nagorno-Karabakh region.