Russian Foreign Minister Sergey Lavrov called for an immediate ceasefire between Azerbaijan and Armenia on Sunday amid rising civilian casualties in the disputed Nagorno-Karabakh region.
Mr Lavrov said Moscow was ready to help seek a solution to the conflict through the Organisation for Security and Co-operation in Europe.
"The Russian side expressed concern in connection with the increase of casualties among the civilian population," the Foreign Ministry said after Mr Lavrov spoke with Armenian Foreign Minister Zohrab Mnatsakanyan.
The conflict, which has worsened over the past eight days, is the biggest escalation in years in the decades-long dispute over Nagorno-Karabakh.
The breakaway region lies within Azerbaijan, but has been controlled by local ethnic Armenian forces since the early 1990s.
Both sides said the hostilities had spread beyond the territory and accused each other of attacking areas outside Nagorno-Karabakh.
Azerbaijan said on Sunday that Armenian forces had fired rockets at its second city of Ganja, killing one civilian and wounding four.
It and threatened to retaliate against military targets inside Armenia.
Armenia’s Defence Ministry said that “no fire of any kind is being opened from the territory of Armenia in Azerbaijan’s direction".
Nagorno-Karabakh’s leader, Arayik Harutyunyan, confirmed on Facebook he ordered “rocket attacks to neutralise military objects” in Ganja.
His spokesman, Vahram Poghosyan, said the territory’s army destroyed a military airport in Ganja, a claim Azerbaijani officials denied.
Armenian officials accused Azerbaijan of carrying out strikes on Stepanakert and its civilian population.
Mr Harutyunyan said that in response, his forces would target “military facilities permanently located in major cities of Azerbaijan.”
Nagorno-Karabakh officials have said nearly 200 servicemen on their side have died so far.
Azerbaijani authorities have not given details on their military casualties, but said 22 civilians were killed and 74 wounded.
The conflict shows little sign of slowing down.
Last week leaders of both countries resisted international pressure for talks.
On Sunday, Azerbaijan's President Ilham Aliyev demanded that Armenia set a timetable for withdrawing from Nagorno-Karabakh and surrounding Azeri territories, and said Azerbaijan would not cease military action until that happened.
