Washington called on Azerbaijan to halt the military action it launched into Armenian-controlled Nagorno-Karabakh on Tuesday, while Russia urged both sides in the conflict to stop the bloodshed in the mountainous and disputed region.
After months of rising tensions in the Armenian-controlled Nagorno-Karabakh in the South Caucasus, Azerbaijan sent troops backed by artillery strikes into the region in an attempt to bring the breakaway region to heel.
Karabakh is internationally recognised as Azerbaijani territory, but part of it is run by separatist Armenian authorities who say it is their ancestral homeland.
US Secretary of State Antony Blinken held calls with both Azerbaijani President Ilham Aliyev and Armenia's Prime Minister Nikol Pashinyan, urging Baku to de-escalate the situation.
"I spoke to Azerbaijani President Aliyev today and urged him to immediately cease military actions in Nagorno-Karabakh," Blinken said on social media.
In a readout of the call, the US Department of State said that Aliyev "expressed readiness" to stop hostilities and hold a meeting with representatives of Nagorno-Karabakh.
Blinken told Pashinyan in their call that Armenia has Washington's full support.
Armenia took control of large swathes of territory in a war that unfolded as the Soviet Union collapsed. Azerbaijan took most of it back in a six-week conflict in 2020, ended by a Russian-brokered truce.
It was not clear whether Baku's actions would trigger a full-scale conflict dragging in Armenia, but the fighting in Karabakh could alter the geopolitical balance in the South Caucasus.
RUSSIA AND THE SOUTH CAUCASUS
Russia - distracted by its own war in Ukraine - is seeking to preserve its influence in the region, crisscrossed with oil and gas pipelines, in the face of greater activity from Turkey, which backs Azerbaijan.
Karabakh separatist authorities said 27 people had been killed, including two civilians, and more than 200 injured due to Baku's military action on Tuesday. Residents of some villages had been evacuated, they said.
Moscow called early on Wednesday on both sides to stop the bloodshed and hostilities and return to the implementation of the 2020 ceasefire agreement.
"We urge the conflicting parties to immediately stop the bloodshed, stop hostilities and eliminate civilian casualties," Russia's foreign ministry said in a statement posted on its Telegram messaging platform.
Relations between Russia and Armenia - traditional allies - have frayed badly since President Vladimir Putin launched the invasion of Ukraine in 2022 and further deteriorated in recent months over what Yerevan says is Moscow's failure to fully uphold the 2020 ceasefire deal.
Yerevan, which had been holding periodic peace talks with Azerbaijan, including questions about Karabakh's future, condemned Baku's "full-scale aggression" against the people of Karabakh and accused Azerbaijan of shelling towns and villages.
Baku said its intention was to "disarm and secure the withdrawal of formations of Armenia's armed forces from our territories, (and) neutralise their military infrastructure".