Nagorno-Karabakh’s armed forces on Friday claimed to have killed seven Azerbaijani soldiers in two overnight commando raids which they said were aimed at thwarting fresh Azerbaijani ceasefire violations along “the line of contact.”

Azerbaijan’s Defense Ministry confirmed one of the raids reportedly carried out at a frontline section in northeastern Karabakh. But it insisted that none of its soldiers died in the fighting. According to the APA news agency, the ministry said Karabakh Armenian forces themselves suffered casualties while being repelled by Azerbaijani troops, a claim denied by the military authorities in Stepanakert and Yerevan.

In a statement, the Karabakh Defense Army said its “preemptive” operation left four Azerbaijani commandos dead. It claimed that they were about to attack Defense Army positions in Karabakh’s northern Martakert district.

According to the statement, the three other Azerbaijani servicemen were shot dead at another frontline section after firing live rounds from an anti-aircraft gun. “During those operations the Armenian side suffered no losses,” added the statement.

The latest fighting is part of a fresh upsurge in Armenian-Azerbaijani truce violations. Two Armenian soldiers, including a lieutenant-colonel, were killed in northeastern Karabakh on Saturday in a reported Azerbaijani ambush. Another Armenian soldier was killed on Tuesday.

Armenia’s defense ministry said on Monday that Baku will face “severe consequences” of the latest escalation.

Tensions in the conflict zone rose sharply in January, leading Armenian President Serzh Sarkisian to threaten “asymmetric” retaliatory strikes against Azerbaijani military targets. The U.S., Russian and French co-chairs of the OSCE Minsk Group seemed to hold Baku primarily responsible for that upsurge in a joint statement issued later in January.

The mediators urged the conflicting parties to “strictly adhere to the ceasefire” after visiting Baku, Stepanakert and Yerevan from February 16-19. A February 20 statement by them said Sarkisian and Azerbaijani President Ilham Aliyev “agreed to consider proposals from the Co-Chairs that could strengthen the ceasefire.” Fighting around Karabakh and along the Armenian-Azerbaijani border eased in the following days.