By Andrew Osborn
LONDON (Reuters) -Azerbaijan launched "anti-terrorist activities" in the Nagorno-Karabakh region to restore constitutional order and drive out what it called Armenian military formations there, a move that could foreshadow a new war in the region.
Loud shelling was audible from unverified social media footage filmed in Stepanakert, the capital of Karabakh, called Khankendi by Azerbaijan, on Tuesday.
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 "high-precision weapons" and not civilians as part of what it called a drive to "restore the constitutional order of the Republic of Azerbaijan."
Civilians were free to leave by what it called humanitarian corridors, it added, including one to Armenia.
Armenia, which says its armed forces are not present in Karabakh, said in a statement via its defence ministry that the situation on its own border with Azerbaijan was stable.
Internationally recognised as part of Azerbaijan, Karabakh 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, but ethnic Armenian authorities who see the area as their ancestral homeland, remained in control of part of Karabakh, including its capital.
A ceasefire deal brokered by Russia and enforced by Russian peacekeepers has remained fragile ever since though with frequent shelling and mutual accusations.
Armenia has accused Moscow, which is embroiled in its own war in Ukraine, of being too distracted to be able to guarantee its security.
Russia's foreign ministry said it was in contact with Azerbaijan and would make a statement soon.
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 said it had informed Russia's peacekeeping force along with a Turkish-Russian monitoring centre which is meant to help ensure the 2020 ceasefire is upheld.
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.
(Reporting by Reuters, writing by Andrew OsbornEditing by Guy Faulconbridge)