Armenian forces killed an Azerbaijani soldier on Saturday in a fresh border clash between foes locked in longstanding conflict over the disputed Nagorny Karabakh region, officials in Baku said.

"Lieutenant Bakhyshly Allahverdy, 23, was killed as Armenian forces violated a ceasefire and shelled Azerbaijani army positions on September 27," Azerbaijan's defense ministry said in a statement.

Azerbaijani troops killed an ethnic Armenian soldier in fresh clashes on Thursday with fighters from the breakaway Nagorny Karabakh region, the rebel defence ministry said.

Russian President Vladimir Putin said he believed there is sufficient good will to resolve the Karabakh conflict as he hosted Sunday the leaders of arch-foes Armenia and Azerbaijan.

At the meeting with Azerbaijan's President Ilham Aliyev and Serzh Sarkisian of Armenia, Putin expressed satisfaction that both leaders had expressed their commitment to seek a peaceful resolution of a conflict that has dragged on for a quarter of a century.

Russian President Vladimir Putin began talks on Saturday with the leaders of arch-foes Armenia and Azerbaijan after recent clashes that have left 22 soldiers dead and fueled fears that one of the bloodiest post-Soviet wars is restarting.

Putin held separate talks at his residence in Russia's southern Black Sea resort town of Sochi with Azerbaijan's President Ilham Aliyev and Serzh Sarkisian of Armenia. A trilateral meeting was due to be held on Sunday.

Russia's President Vladimir Putin will host talks this week between the leaders of Armenia and Azerbaijan in a bid to quell a surge of violence over the disputed Nagorny Karabakh region, Moscow said Monday.

At least 18 Azerbaijanis and ethnic Armenians have died in recent days in the most serious bout of hostilities over the breakaway region in two decades.

Azerbaijan said Saturday it had lost four troops in new clashes with arch-foe Armenia near the disputed Nagorny Karabakh region as mediators sounded the alarm over a spike in tensions in the protracted conflict.

The fresh confrontations -- which also led to the death of an ethnic Armenian soldier -- come after Azerbaijan said Friday that eight troops had been killed in three days of fighting, with Moscow and Washington both expressing concern over the violence.

Azerbaijan said Friday it had lost eight soldiers in three days of clashes with arch-foe Armenia near the disputed Nagorny Karabakh region in a dramatic spike in tensions in the long-simmering territorial conflict.

Azerbaijan's defense ministry said Armenian troops had ramped up their activity in the past few days and attacked Azeri positions.

Azerbaijani authorities said Thursday that prominent human rights activist Leyla Yunus, who has been charged with treason, was collaborating with the spy agencies of arch-enemy Armenia.

"It is established that in 2002 Leyla Yunus and her husband Arif Yunus... had trained the journalist Rauf Mirkadirov in espionage and has since organized several of his trips to Armenia," the Azeri prosecutor general's office said in a statement.

Azerbaijani forces shot dead an Armenian soldier in frontline clashes in the disputed Nagorny Karabakh region on Saturday, the breakaway defense ministry said.

"A 20-year-old soldier, Khachatur Badasian, suffered a fatal gunshot wound" after Azerbaijani special forces "attempted an incursion to carry out sabotage and spying" in the early hours of Saturday, the ministry said.

Azerbaijani troops killed an Armenian farmer in the latest violent confrontation along the disputed Nagorny Karabakh region's volatile frontline, rebel authorities said on Tuesday.

"On July 14 (Monday), Azerbaijani troops shot dead a resident of Karabakh's Askeran district, Arvind Danielyan," the separatist region's prosecutor general said in a statement.