U.S., Russian and French mediators on Tuesday voiced serious concern at Azerbaijani armed incursions reported by the Armenian side and urged Azerbaijan to seek only a peaceful settlement of the Nagorno-Karabakh conflict.

The three diplomats co-heading the OSCE Minsk Group met with Azerbaijani Foreign Minister Elmar Mammadyarov in Krakow, Poland to discuss recent weeks’ upsurge of fighting in the conflict zone that has left at least a dozen soldiers from both sides dead. In an ensuing joint statement, they seemed to hold Baku primarily responsible for the latest escalation.

“We expressed to the Minister our serious concern about reported incursions across the Line of Contact and the Armenia-Azerbaijan border, resulting in casualties,” read the statement. “The rise in violence that began last year must stop for confidence to be restored and progress to be made in the Nagorno-Karabakh peace process. We called on Azerbaijan to observe its commitments to a peaceful resolution of the conflict.”

“We also call on Armenia to take all measures to reduce tensions. All sides must abide by the terms of the ceasefire agreement. Violence undermines efforts to bring about peace,” said the Minsk Group co-chairs.

“We reminded the Minister of our mandates and expressed concern about voices critical of the ongoing negotiation process, the role of the Minsk Group Co-Chairs, and the duties of OSCE monitors,” they added in an apparent reference to periodical criticism of the mediators voiced by Azerbaijani leaders.

Azerbaijan’s President Ilham has repeatedly denounced the mediating powers for not helping his country regain control over Karabakh and Armenian-controlled districts surrounding it.

The Azerbaijani government did not immediately react to the extraordinary criticism. In a statement on the Krakow meeting cited by the APA news agency, the Azerbaijani Foreign Ministry cited Mammadyarov as telling the mediators that the Armenians themselves have launched commando raids on the frontlines. He also stuck to the official line that the conflict’s resolution should start from “the withdrawal of Armenia’s troops from Azerbaijan’s occupied territories.”

In their statement, the co-chairs said they also emphasized to Mammadyarov “the importance of measures aimed at avoiding unintended incidents along the Line of Contact and Armenia-Azerbaijan border.”

One such measure for years advocated by the mediating troika is a mutual withdrawal of snipers from all frontline positions. Armenian Defense Minister Seyran Ohanian reaffirmed Yerevan’s strong support for the idea earlier on Tuesday. The Azerbaijani Defense Ministry was quick to again reject it.

“Sniper withdrawal from the frontlines is a sick idea of the Armenian side,” Haqqin.az quoted an Azerbaijani Defense Ministry spokesman as saying.