Azerbaijan said Armenian forces had killed three of its troops on Monday, as clashes over the disputed region of Nagorny Karabakh continued for a third day despite international pressure to stop fighting.
The Azeri defence ministry said three servicemen were killed when Armenians shelled their positions using mortars and grenade launchers.
"In the event of continued Armenian provocations, we will launch a full-scale operation along the entire front line, using all kinds of weapons," ministry spokesman Vagif Dargahly told journalists.
Separately, the rebels, in a statement from their unrecognised capital of Stepanakert in Nagorny Karabakh, said Azeri troops "intensified shelling of the Karabakh army positions on Monday morning, using 152-millimetre mortars, rocket-propelled artillery and tanks."
In the Armenian capital of Erevan, defence ministry spokesman Artsrun Hovhannisyan said the rebels "seriously advanced at certain sectors of the front line and took up new positions."
The report was quickly dismissed as "untrue" by Azerbaijan.
Its defence ministry said it was in control of several strategic heights in Karabakh that were captured by Azeri troops on Saturday.
Russia and the West appealed to all sides for restraint after the fighting -- the worst outbreak of violence in decades over the disputed territory -- erupted on Friday night.
At least 33 troops and two civilians have died.
On Sunday, Azerbaijan said it had decided to "unilaterally cease hostilities" and pledged to "reinforce" several strategic positions it claimed to have captured inside the Armenian-controlled territory.
The authorities in Karabakh -- which claims independence but is heavily backed by Armenia -- said they were willing to discuss a ceasefire but only if it saw them regain their territory.
Ethnic Armenian separatists backed by Yerevan seized control of the mountainous Nagorny Karabakh region in an early 1990s war that claimed some 30,000 lives. The foes have never signed a peace deal despite the 1994 ceasefire.
Energy-rich Azerbaijan, whose military spending exceeds Armenia's entire state budget, has repeatedly threatened to take back the breakaway region by force if negotiations fail to yield results.
Moscow-backed Armenia says it could crush any offensive.