Armenia's caretaker Prime Minister Nikol Pashinian has accused Azerbaijani troops of crossing the southern border and trying to stake claim to territory.
Last year the two archfoes went to war over the breakaway region of Nagorno-Karabakh and the ensuing six-week conflict claimed thousands of lives and ended with a Moscow-brokered truce that saw Armenia ceding swaths of territory that it had controlled for decades.
Pashinian resigned last month after being subjected to huge political pressure over his handling of the conflict. He is currently staying on in a caretaker capacity, setting the stage for June 20 parliamentary elections.
Pashinian on May 13 accused Baku of new transgressions as he convened an emergency meeting of his Security Council.
He cited the "explosive situation" in Armenia's southeastern Syunik Province, where Azerbaijani troops reportedly advanced several kilometers into Armenian territory early on May 12 and refused to pull back.
The Armenian Defense Ministry said later on May 13 that Azerbaijani forces also breached two other sections of the Armenian-Azerbaijani border.
It said Armenian Army units deployed there stopped their advances and demanded that they immediately retreat to the Azerbaijani side of the border.
Pashinian claimed that a total of about 250 Azerbaijani soldiers currently remain within Armenia’s internationally recognized borders. He said that they are using “false maps” to lay claim to that territory.
"It is an encroachment on the sovereign territory of the Republic of Armenia," Pashinian said. "This is an act of subversive infiltration."
Pashinian instructed his defense and foreign ministers to ask the Russian-led Collective Security Treaty Organization, of which Armenia is a member, to invoke Article 2 of its founding treaty, which commits the bloc to discussing a collective response to grave security threats facing its member states.
He invoked the need for "preventing a further escalation of the situation and protecting the territorial integrity, stability, and sovereignty" of Armenia.
Azerbaijan has not commented on the accusations.
The United States -- one of the three countries in the so-called Minsk Group that leads diplomacy on Nagorno-Karabakh -- said it was "closely following" the rising tensions.
"We understand communication between the parties is ongoing and urge restraint in de-escalating the situation peacefully," State Department spokesman Ned Price tweeted.