Armenia said on Tuesday that the ceasefire with arch-foe Azerbaijan over the breakaway region of Nagorno Karabakh virtually no longer exists, describing frequent skirmishes at the frontline as "war".

The defense ministry's strongly-worded statement came after talks in Switzerland at the weekend between the leaders of Azerbaijan and Armenia, Ilham Aliyev and Serzh Sargsyan, over the future of the disputed region appeared to have brought no tangible results.

"What we have today is a war," Armenia's defense ministry spokesman Artsrun Hovhannisyan told journalists.

"We must use the word 'war' as there is no ceasefire anymore," he added, accusing Azerbaijan of military provocations along the ex-Soviet neighbours' shared border and across the Karabakh frontline.

"Azerbaijan is using all existing armaments: tanks, howitzers, and anti-aircraft artillery."

Ethnic Armenian separatists backed by Yerevan seized control of the mountainous Nagorno Karabakh region, which was part of Azerbaijan during the Soviet period, during a war the early 1990s which claimed the lives of some 30,000 people.

A 1994 ceasefire failed to lead to a peace deal, with clashes erupting regularly and the two countries remaining on a war footing.

Azerbaijan responded to the statement with counter-accusations, blaming Armenia for the recent escalation.

"Ceasefire violations are taking place because of the illegal presence of Armenian forces in the occupied lands of Azerbaijan," Azerbaijan's Foreign Ministry spokesman Hikmat Hajiyev told AFP.

"Armenia has to withdraw from the seized lands ... only afterwards the sustainable peace can be guaranteed in the region."

In recent months there has been an unprecedented escalation of the conflict, and the Organization for Security and Cooperation in Europe (OSCE) mediators recently warned "the status quo has become unsustainable".

Earlier this month, Azerbaijani tanks shelled positions in Nagorno Karabakh region for the first time in more than 20 years, the rebel defense ministry said.

Energy-rich Azerbaijan, whose military spending exceeds Armenia's entire state budget, has repeatedly threatened to take back the breakaway region by force if negotiations fail to yield results.

Moscow-backed Armenia says it could crush any offensive.