Armenia and Azerbaijan blamed each other for an exchange of fire in a border area on Thursday in which Azerbaijan said one of its soldiers was killed.
The clashes come amid an intensification of diplomatic talks between the two South Caucasus rivals aimed at bringing them back from the brink of another all-out conflict over the disputed Nagorno-Karabakh region.
The enclave is internationally recognised as part of Azerbaijan, but populated mainly by ethnic Armenians and has been the centre of a decades-long dispute.
Baku last month installed a checkpoint at the start of the Lachin Corridor - the only road route linking Armenia to Karabakh - in a move that Yerevan said was a "gross violation" of a Russian-brokered 2020 ceasefire agreement.
In Thursday's clash, the latest in a series of border flare-ups, both sides said they were acting in self-defence and blamed the other for firing first.
Azerbaijan said Armenian forces had staged a "deliberate provocation" and had killed one Azerbaijani soldier. Armenia's defence ministry said four of its soldiers were wounded after Azerbaijan shelled its positions near the village of Sotk on their shared border.
Armenian Prime Minister Nikol Pashinyan said the incident was an attempt by Azerbaijan to disrupt ongoing peace talks between the sides.
The foreign ministers of both countries met in Washington for four days of talks at the start of May that did not yield a breakthrough. Pashinyan is set to meet Azerbaijani President Ilham Aliyev in Brussels on May 14 for EU-brokered talks aimed at cooling tensions.
The latest clashes are also seen as a test of Russia's ability to influence events in the South Caucasus.
Russia is a formal ally of Armenia through a mutual self-defence treaty, but also strives for good relations with Baku. Moscow says the 2020 peace accord it brokered to end a six-week war that killed thousands is the only basis for a long-term solution.
Kremlin spokesman Dmitry Peskov called for both sides to show restraint and said Moscow's diplomatic contacts with both Yerevan and Baku were continuing. But there are no plans for Russian President Vladimir Putin to speak to Pashinyan or Aliyev directly, Peskov said.
(Reporting by Jake Cordell in TbilisiEditing by Gareth Jones)
