Baku said 12 Armenian and four Azeri soldiers were killed, accusing Yerevan of provoking the shootout.

A spokesman for pro-Armenian forces in Nagorno-Karabakh said two of its troops were wounded and eight Azeri soldiers killed in the clashes started by Baku.

Pro-Armenian troops seized Azerbaijan's region during the war in the 1990s.

If confirmed, the fighting was heavier than most of the skirmishes that often break out along a ceasefire line that was agreed in 1994.

On Tuesday, Azeri authorities told the BBC that Armenia had provoked the clashes to divert attention from its domestic problems.

Eight people died during clashes with police in the Armenian capital Yerevan on Saturday, after disputed elections in February.

Armenia and Azerbaijan still technically remain at war with each other.

Earlier this week, Azerbaijan's President Ilham Aliyev said Baku was ready to re-take the region by force, and had been buying the military hardware and ammunition to do so.

Some 30,000 people were killed and more than one million fled their homes during several years of fighting.

Agencies