According to the Karabakh Defense Ministry, the incident was triggered by a reconnaissance mission by some 20 Azerbaijani servicemen behind the Line Of Contact separating Azerbaijani and Armenian forces.
Armenia launched a retaliation attack during the night of June 20-21 on Azerbaijani positions in Fizuli, southeast of the disputed enclave, killing one Azerbaijani serviceman. Of the seven Azerbaijani districts contiguous to Nagorno-Karabakh currently occupied by Armenian forces, Fizuli is one of the two that Baku is reportedly demanding should be the first to be returned to Azerbaijani control.
The Minsk Group co-chairs termed the June 18 attack, which took place the day after they met in Moscow with Azerbaijani President Ilham Aliyev to discuss a peaceful solution to the conflict, as "an unacceptable violation of the 1994 Cease-Fire Agreement and...contrary to the stated commitment of the sides to refrain from the use of force or the threat of the use of force. The use of military force at this juncture "can only be seen as an attempt to damage the peace process," they said.
The EU's special representative for the South Caucasus, Ambassador Peter Semneby, for his part described the attack to RFE/RL's Armenian Service on June 21 as "a deplorable event" that "should not have taken place." He further expressed regret for the "unnecessary tragic loss of life."
Azerbaijani Foreign Ministry spokesman Elhan Polukhov said the June 18 clash was the direct consequence of Armenia's failure to withdraw from occupied Azerbaijani territory. He said the way to avoid a reoccurrence is for Armenia "to sit down at the negotiating table and continue talks on the basis of the updated Madrid principles," which he implied Armenia is unwilling to do.
Richard Giragosian, director of the Armenian Center for National and International Studies (ACNIS) in Yerevan, said that while the June 18 attack fits into "a consistent pattern of limited skirmishes and probes, especially Azerbaijani probing the defensive positions on the Armenian side," it was nonetheless the most serious cease-fire violation in the past two years.
Citing unidentified Armenian military sources, he said the attack must have been prepared over a period of several days. He described it as more professional and more deadly than previous such incursions. The attack began with an Azerbaijani sniper inflicting a fatal head wound on an Armenian soldier on the front line.
Giragosian said the Armenian military anticipates an intensification of Azerbaijani military activity in coming months.
*UPDATE: It has been brought to my attention that I appear inadvertently to have misrepresented the statement by the OSCE Minsk Group co-chairs that condemned the violent incident, but did not blame Azerbaijan for starting it. The statement further called on the sides to "exercise restraint" and "prepare their population for peace." The blog post has been updated to reflect that.