The European Union‘s border monitoring mission in Armenia said Tuesday that one of its patrols had come under fire on the volatile frontier with Azerbaijan, which denied responsibility for the incident.

“No EUMA member was harmed,” the EU Mission in Armenia said on social media, confirming that its personnel were “present to the shooting incident in our area of responsibility”.

The statement came after Armenia said Azerbaijan’s military had opened fire on the observers monitoring the border between the two countries, where tensions have been spiralling.

Yerevan’s defence ministry said the gunfire took place as the EU observers patrolled the village of Verin Shorzha, about four miles (six kilometres) from the Azeri border. It also reported no casualties.

Azerbaijan said that the claims amounted to disinformation and that Baku is warned in advance of the patrols.

The EU, which began its border monitoring mission earlier this year, has taken on a broader mediation role between the two countries as they deal with disputes over the mountainous territory of Nagorno-Karabakh.

The EU’s growing diplomatic engagement in the Caucasus has irritated Russia, a regional power broker.

Also on Tuesday, Russian Foreign Minister Sergei Lavrov urged Azerbaijan to open a key corridor that links Nagorno-Karabakh to Armenia, his ministry said in a statement.

In a call with his Azerbaijani counterpart Jeyhun Bayramov, Lavrov said Baku should implement agreements to de-escalate growing tensions with Armenia.

He also emphasised the need for “the unblocking of humanitarian routes, including the Lachin corridor”.

The tensions between Baku and Yerevan have escalated sharply in recent days, as each side accuses the other of cross-border gunfire and violating agreements.