Armenian troops killed an Azerbaijani soldier in the latest border clash between the arch-foes locked in conflict over the disputed Nagorny Karabakh region, officials in Baku said Thursday.

"On the evening of March 11 (Wednesday) an Armenian army reconnaissance group attempted an attack on Azerbaijani positions and was repelled after fierce fighting," Azerbaijan's defence ministry said in a statement.

Azerbaijan authorities said Wednesday they had arrested six men accused of being Islamic militants and planning "terrorist acts" in the mainly Shiite Muslim country.

The ex-Soviet nation's security ministry said in a statement that the men were planning to sow disorder with the aim of establishing "a sharia-based state in Azerbaijan."

Locals sigh with relief as their Armenian village of Movses, close to the border with Azerbaijan, disappears in the lilac mist rolling down from the Kardash mountain, where Azeri snipers have fortified positions.

"The mist is our salvation. When visibility is zero, we know the Azeris won't be shooting," said Khanum, an elderly Armenian woman who, like other Movses residents, lives in constant fear of Azeri snipers.

An ethnic Armenian soldier from the separatist Nagorny Karabakh region was killed Tuesday by Azerbaijani troops in a fresh clash along the breakaway region's frontier, the rebel authorities said.

"Serviceman Arsen Karapetyan, 20, was mortally wounded when Azerbaijani forces violated the ceasefire at the Karabakh frontline," Karabakh's defence ministry said in a statement.

Three people were killed in renewed clashes between Azerbaijani and Armenian forces over the disputed Nagorny Karabakh region, officials from both countries said Friday.

The victims included an Armenian civilian killed in his courtyard by Azerbaijani shelling on villages along the Karabakh border, Armenian defense ministry spokesman Artsrun Hovannisian told AFP.

The OSCE called Tuesday on Armenia and Azerbaijan to end deadly fighting in the disputed region of Nagorny Karabakh where four Armenian soldiers were reportedly killed this month.

"I would like to urge the sides to ensure a full ceasefire and cessation of hostilities," said Ivica Dacic, foreign minister of Serbia, the security body's current chair.

An Azerbaijan court on Tuesday extended by nearly two months the pretrial detention of a prominent investigative journalist and anti-graft campaigner, her lawyer said.

The journalist Khadija Ismayilova's "pre-trial detention was extended by one month and 19 days," her lawyer Ialchin Imanov told AFP.

Armenian President Serzh Sarkisian on Monday threatened arch-foe Azerbaijan with an "asymmetrical" response to any attempt to use military means in resolving their long-standing conflict over the disputed Nagorny Karabakh region.

"Until now we were reacting symmetrically ... from now on we could take asymmetrical actions," Sarkisian told a televised meeting with Armenia's defense ministry.

Azerbaijani forces on Wednesday killed two Armenian soldiers in clashes with Armenian troops, officials  said as tensions escalated over the disputed Nagorny Karabakh.

"Azerbaijani armed forces attempted to attack Armenia's defensive positions" at the Karabakh front line, the breakaway region's defense ministry said in a statement.

Azeri troops killed an Armenian soldier in a Saturday border clash, the latest in the long-running conflict between the two countries, Yerevan said.

The violence took place near the northeastern Armenian city of Voskevan, the Armenian defense ministry said.