Visiting US Secretary of State Hillary Clinton has said she is "deeply concerned" about continuing clashes between Armenia and Azerbaijan.
Speaking after talks in Baku, she again warned of the threat of an escalation, which "could have unpredictable and disastrous consequences".
Five Azerbaijani and three Armenian soldiers were killed this week.
A further Armenian fighter was killed on Wednesday in the disputed territory of Nagorno-Karabakh, Armenians said.
They accused Azerbaijani troops of attempting an incursion into the enclave early on Wednesday, and say two other Armenian fighters were wounded as they beat off the alleged attack.
Azerbaijan and Armenia, both former Soviet republics, fought a war over the enclave in the early 1990s which left some 30,000 people dead, and displaced hundreds of thousands.
Fighting this week, on the border between Tavush in Armenia and Qazax in Azerbaijan, was among the fiercest seen in recent years.
Speaking after talks with Azerbaijani President Ilham Aliyev, Mrs Clinton said: "This cycle of violence and retaliation must end."
Together with Russia and France, the US co-chairs the Minsk Group, set up by the Organization for Security and Co-operation in Europe after the 1994 ceasefire in Karabakh to help resolve the conflict.
Addressing Azerbaijan's widely criticised human rights record, Mrs Clinton urged the government "to respect their citizens' right to express views peacefully, [and] to release those who have been detained for doing so", according to the Reuters news agency.
Mrs Clinton also paid tribute to Azerbaijan's role as an energy provider. Caspian Sea pipelines cross its territory, bringing oil to southern Europe.
She said she appreciated "the central role that Azerbaijan plays in efforts to diversify supplies of oil and gas as well as the routes over which they are transported".