Azerbaijan says it has launched a military operation in Karabakh almost three years after it went to war with Armenia over the disputed mountainous region.
Blasts were heard Tuesday in the Armenian separatist stronghold of Khankandi which Armenians call Stepanakert in the breakaway region.
They said Karabakh towns and cities were “under intensive fire”.
"Mass shelling has started here," Ruen Vardanyan, a former state minister of Karabakh said on Telegram.
Baku said it had informed the command of Russian peacekeepers and leadership of Turkish-Russian monitoring center about military activities it was carrying out in Karabakh.
Its foreign ministry said the Karabakh separatist “regime” must be dissolved.
Russia said it was in contact with Azerbaijan over the operations. Foreign ministry spokeswoman Maria Zakharova urged the two South Caucasian countries to "end bloodshed" and pursue peace talks.
"The Russian side urges an end to the bloodshed... and a return to a peaceful settlement," she said.
Zakharova said "all steps for a peaceful solution are spelled out in (Moscow-brokered) agreements signed between 2020 and 2022."
The developments come after months of mounting tensions between the Caucasus neighbors and hours after Baku said six Azerbaijanis were killed by mine explosions in Karabakh, blaming Armenian separatists.
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.
Azerbaijan said Tuesday it had opened humanitarian routes for non-combatants to flee hostilities.
"To ensure the evacuation of the population from the risk zone, humanitarian corridors and reception points have been established on the Lachin road and in other directions," the defense ministry said in a statement.
"Localized anti-terrorist measures have been launched in the region," it said, adding it was using "high precision weapons on the front line and in depth as part of the operations.
Armenia's defense ministry said the situation on its border with Azerbaijan was stable.
Armenia and Azerbaijan have been locked in a decades-long conflict over Karabakh, going to war in the 1990s and in 2020.
The breakaway region populated by Armenians since 1990 is internationally recognized as part of Azerbaijan.
Baku has cited "systemic shelling" of Azerbaijani positions by Armenian separatists in Karabakh as well as "the continuing mining of our territories" and accused Yerevan of a troop buildup.
It said it had "repeatedly warned" of what it called violations of a Russian-brokered ceasefire that ended a 2020 war between the neighbors, calling them "a serious source of threat for peace and stability in the region."
Baku said it wanted to "suppress large-scale provocations" in Karabakh. Its aims also included the "disarmament and withdrawal of the Armenian armed forces from our territories" and "the safety of the civilian population" returning to territories it reclaimed in 2020.
Armenia denied that its troops were present in Karabakh. "The Armenian defense ministry has repeatedly stated, and states again, that the Republic of Armenia has no army in Nagorno-Karabakh," it said.
Hours earlier, Baku said four policemen and two civilians were killed in mine explosions staged by "Armenian separatist groups."
In a six-week war in 2020, Azerbaijan regained control of pockets of Karabakh with fighting ending with a Russian-brokered peace deal.