-Azerbaijan's Defense Ministry says four of its troops have been killed near the breakaway region of Nagorno-Karabakh.
The ministry said in a statement that the four were killed on August 2 in a clash with "Armenian sabotage groups" conducting an operation in the Agdam-Terter area.
The statement said Azerbaijani units repelled the attack.
A ministry official told RFE/RL that "Azerbaijani military jets are conducting maneuvers to protect the homeland."
Asked about reports of troop movements toward the Armenian border, the official responded that "to protect Azerbaijan's territorial integrity, the military can and will move troops and hardware within its own jurisdiction."
The self-styled Ministry of Defense of Nagorno-Karabakh meanwhile said on August 2 that its forces killed at least seven Azerbaijani troops and lost one serviceman overnight in what it described as a successful repulsion of an attack by Azerbaijani commando units.
It also reported attacks by Azerbaijani troops in several other directions, all of which, it said, had been successfully repelled without further casualties.
Meanwhile, the Armenian Defense Ministry on August 2 again blamed Azerbaijan for the escalation of violence around Nagorno-Karabakh.
In a statement it said that, in recent days, Azerbaijani armed forces have been making attempts to overrun Armenian positions and conduct subversive activities.
It accused Azerbaijan of using large-caliber guns and artillery, and of increasingly shelling populated areas.
An RFE/RL correspondent reporting from the northeastern province of Armenia said on August 2 that the situation at the border with Azerbaijan remains tense.
The correspondent says Armenian positions regularly come under fire. Intensive fire was, in particular, heard near the border village of Berkaber.
Exchanges of fire between Azerbaijani and Armenian forces on the Karabakh frontline have become more frequent in recent days.
Azerbaijan's Defense Ministry said on August 1 that Armenian troops had attacked Azerbaijani positions and killed eight Azerbaijani troops over the previous three days.
On July 31, Nagorno-Karabakh authorities said that two of their troops were killed in an attack by Azerbaijani forces.
Azerbaijan and Armenia have been locked in a conflict over Azerbaijan's breakaway region of Nagorno-Karabakh for years.
Nagorno-Karabakh, populated mainly by ethnic Armenians, declared independence from Azerbaijan after a 1988-94 war that claimed an estimated 30,000 lives and displaced hundreds of thousands of people.
Internationally mediated negotiations with the involvement of the Organization for Security and Cooperation in Europe's so-called Minsk Group have failed to result in a resolution.
The Minsk Group is co-chaired by France, Russia, and the United States.
Russia's Foreign Ministry on August 2 expressed concern over the flare-up of violence in Nagorno-Karabakh, and said "any further escalation is unacceptable."
On August 1, the United States called on the sides "to take immediate action to reduce tensions and respect the cease-fire."
State Department deputy spokeswoman Marie Harf said in a statement that Washington is urging the leaders of Armenia and Azerbaijan to meet "at the earliest opportunity to resume dialogue on key issues."
Harf said the United States remains "committed to participating in the Minsk Group process and stands ready to help efforts to bring about a lasting settlement."