Azerbaijan said on Tuesday its armed forces had launched what it called "local anti-terrorist activities" in the Nagorno-Karabakh region to restore constitutional order by disarming and forcing the withdrawal of Armenian military formations there.
Karabakh, internationally recognised as part of Azerbaijan, has an overwhelmingly ethnic Armenian population and broke from Baku's control in the early 1990s after a war. Azerbaijan recaptured swathes of land in and around it in a 2020 war.
Azerbaijan's defence ministry spoke in a statement of its intention to "disarm and secure the withdrawal of formations of Armenia’s armed forces from our territories, (and) neutralise their military infrastructure."
It said it was only targeting legitimate military targets using what it called high-precision weapons and not civilians or civilian infrastructure as part of what it called a drive to "restore the constitutional order of the Republic of Azerbaijan."
It said it had informed a Russian peacekeeping force in the area along with a Turkish-Russian monitoring centre which is meant to help ensure a 2020 ceasefire is upheld.
Armenia says it does not have any military personnel in Karabakh and that its priorities are purely humanitarian. Much of Karabakh is controlled by ethnic Armenian authorities whom Baku has long been pressuring to disband and disarm.
Ruben Vardanyan, a billionaire banker who was a top official in Karabakh's ethnic Armenian administration until February, wrote on X, formerly known as Twitter:
"Azerbaijan has initiated a massive artillery attack against Nagorno Karabakh, targeting cities and civilians on a large scale."
Reuters could not immediately verify assertions from either side.
Baku announced its operation after complaining that six of its citizens had been killed by land mines in two separate incidents, something it blamed on "illegal Armenian armed groups."
The escalation occurred a day after badly needed food and medicine was delivered to Karabakh along two roads simultaneously, a step that looked like it could help ease mounting tension between Azerbaijan and Armenia.
Until the last few days, Baku had imposed sweeping restrictions on the Lachin corridor - the only road linking Armenia with Karabakh - and had not allowed in aid on the grounds that the route was purportedly being used for arms smuggling.
Armenia had said that Baku's actions, which is said had caused a humanitarian catastrophe, something Azerbaijan denied, were illegal.
Armenia's foreign ministry had said on Monday that Azerbaijan's diplomatic stance looked like it was preparing the ground for some kind of military action, Reuters reports.