Armenia and Azerbaijan on Tuesday traded accusations of opening fire along their volatile shared border, the latest flare-up in tensions between the Caucasus arch foes despite ongoing peace talks.

The two countries' leaders have repeatedly expressed optimism about the prospect of reaching a lasting peace deal but lingering territorial disputes between the historic enemies pose a constant risk of a renewed conflict.

Azerbaijan's defence ministry said "units of the Armenian armed forces on April 1 opened fire with small arms at Azerbaijani army positions" near the Nakhchivan Autonomous Republic, an Azerbaijani exclave along the border with Iran and southern Armenia.

Armenia's defence ministry said the claim "doesn't correspond to reality" and accused Baku of firing first.

"Azerbaijani armed forces units opened fire on Armenian combat positions on April 1 at 10:00 am in Kut ... and on April 2 at 12:40 am in Tegh," the ministry said, referring to two different areas on the countries' shared border.

The claims of fresh clashes come after Azerbaijan accused Armenia on Monday of "concentrating manpower, armoured vehicles, artillery installations, and other heavy firepower" near the border.

Azerbaijan said it had observed "intensive movement of (Armenia's) troops in different directions."

"We warn that in case of any attempt at a military provocation by the Armenian armed forces against Azerbaijan, it will be resolutely suppressed by the Azerbaijan army," Baku said.

Armenia denied the accusations. Its defence ministry said its military had been conducting "purely defensive engineering works within its sovereign territory".

Armenian Prime Minister Nikol Pashinyan and Azerbaijani President Ilham Aliyev have said a comprehensive peace agreement is within reach after Baku recaptured the breakaway Nagorno-Karabakh region from Armenian separatists last year in a lightning military offensive.

The former Soviet republics have fought two wars for control of the mountainous region -- most recently in 2020 and in the 1990s amid the break-up of the Soviet Union -- that have claimed thousands of lives on both sides.

After Baku reclaimed Karabakh in a one-day offensive in September last year, the enclave's entire ethnic Armenian population -- more than 100,000 people -- fled for Armenia.