Azerbaijan on Wednesday summoned the French ambassador to protest a visit by the leader of the breakaway Nagorny Karabakh region, the Caucasus republic's foreign ministry said.

"France's ambassador to Baku, Pascal Monnier, has been summoned to Azerbaijan's foreign ministry and handed a note of protest over the separatist leader's visit to France on May 17-19," Azerbaijan's foreign ministry spokesman, Hikmet Hajiyev, told AFP.

Opposition parties for the first time won parliamentary seats in the legislature of Azerbaijan's breakaway Nagorny Karabakh in a vote denounced as illegitimate by Baku and the West, preliminary results showed on Monday.

Three pro-regime parties won most of the votes in Sunday's parliamentary elections in the separatist region but in a surprise development two opposition parties cleared the five-percent threshold needed to get into the 33-member legislature, officials said.

Azerbaijan's separatist region of Nagorny Karabakh went to the polls Sunday to elect a new parliament in a vote denounced as illegitimate by Baku and the West.

For over two decades, the Armenia-Azerbaijan dispute over the territory -- which no country recognizes as independent -- has been a major source of tension in the strategic South Caucasus region wedged between Iran, Russia and Turkey.

Armenian forces on Thursday killed an Azerbaijani soldier in the latest breach of a ceasefire between the arch-foes locked in a simmering conflict over the disputed Nagorny Karabakh region, officials in Baku said.

"Armenian forces have yet again violated the ceasefire and killed an Azerbaijan army warrant officer," Azerbaijan's defence ministry said in a statement without giving further details.

Another Armenian soldier was killed this week as clashes intensified between arch-foes Azerbaijan and Armenia, locked in a decades-long dispute over Nagorny Karabakh region, Armenian officials said on Wednesday.

"On April 7 (Tuesday), a soldier was shot dead on the Karabakh frontline by an Azerbaijani sniper," the separatist region's defence ministry said in a statement.

An Azerbaijani sniper shot dead an Armenian soldier, the latest casualty in violence along the breakaway Nagorny Karabakh region's volatile frontline, rebel officials said Monday.

"A Karabakh army serviceman was mortally wounded on Sunday evening by an Azerbaijani sharpshooter," the separatist defense ministry said in a statement.

Armenian forces killed an Azerbaijani soldier as clashes festered along the volatile frontline of the breakaway Nagorny Karabakh region, a military spokesman in Baku said on Friday.

"On March 26 (Thursday) Armenians have violated a ceasefire on the eastern sector of the Karabakh frontline," an Azerbaijani Defense Ministry official told AFP.

Azerbaijani troops on Thursday killed three ethnic-Armenian soldiers from the army of breakaway Nagorny Karabakh, the rebel authorities said as tensions between Baku and Yerevan escalate over the disputed region.

"An Azerbaijani commando unit on Thursday morning attacked Karabakh army positions," Nagorny Karabakh's defense ministry said in a statement.

A court in Azerbaijan on Tuesday sentenced to six years in jail a prominent rights activist's brother who was recognized by Amnesty International as a "prisoner of conscience".

The court for serious crimes in the Azerbaijani capital Baku, "has sentenced Siraj Karimov to six years in prison over trumped-up drug-related charges," his lawyer Nemet Karimov told AFP.

Armenian troops have killed a second Azerbaijani soldier this week, Baku said Friday, threatening a "severe" response to the latest violence in a long-standing conflict over the disputed Nagorny Karabakh region.

"On March 13, the Armenian armed forces violated the ceasefire. An Azerbaijani soldier was shot dead" in the latest border clash between the arch-foes, Azerbaijan's defense ministry said in a statement.