Armenian forces kill five Azerbaijani troops on border
Azerbaijan has accused Armenia of violating its border and shooting dead five of its soldiers, a day after three Armenians were killed in the same area.
Armenian "saboteurs" killed four soldiers in one incident and a fifth Azerbaijani soldier was shot dead in another, the defence ministry said.
But Armenia's defence ministry said its forces had reacted to an attempted crossing by Azerbaijani troops.
Visiting US Secretary of State Hillary Clinton has called for restraint.
She arrived in Georgia on Tuesday from Armenia, with a visit to Azerbaijan scheduled for Wednesday.
A formal ceasefire between Azerbaijan and Armenia since their war over the disputed region of Nagorno-Karabakh is looking increasingly fragile.
A statement from the Azerbaijani defence ministry said an "Armenian sabotage group" had tried to enter Azerbaijani military positions at around 06:30 (0130 GMT) on Tuesday in the village of Asagi Askipara, in the Qazax district of western Azerbaijan.
"However, they sustained casualties and retreated," it said. Four Azerbaijani soldiers were killed in the fighting, it added.
The fifth Azerbaijani soldier was killed in a separate shooting incident in the Qazax district, the ministry said, without giving details.
In its version of events, Armenia's defence ministry accused Azerbaijani forces of attempting an incursion across the border, the second in so many days.
Armenian border guards fought off a group of between 15 and 20 "armed diversionists" trying to "invade Armenian territory" in the Tavush district, which borders Qazax, the ministry said.
Armenia confirmed that it had "neutralised" the Azerbaijani group.
No Armenian soldiers were hurt in the fighting, it added.
On Monday, Armenia accused Azerbaijan of having killed three of its soldiers and wounded six in Tavush.
Azerbaijan's defence ministry denied killing the three soldiers.
The two former Soviet republics fought a bloody war over the disputed region of Nagorno-Karabakh in the 1990s.
A formal ceasefire is now looking increasingly fragile.
Speaking in Armenia on Monday, Mrs Clinton said: "I am very concerned by these incidents and have called on all parties, all actors, to refrain from the use or threat of force.
"There is a danger that it could escalate into a much broader conflict that would be very tragic for everyone concerned."