Sept 13 (Reuters) – Clashes broke out between the troops of Azerbaijan and Armenia, Russian news agencies reported early on Tuesday, in a resumption of decades of hostilities linked to the disputed territory of Nagorno-Karabakh. Azerbaijan, which regained full control of the territory in a six-week conflict in 2020, has acknowledged casualties among its forces. Armenia did not report any casualties but said clashes continued overnight. Yerevan’s government said it would invoke a cooperation agreement with Russia and appeal to a Russian-led security bloc, the Collective Security Treaty Organization, as well as the United Nations Security Council, Interfax reported. Sign up now for FREE unlimited access to Reuters.comSign up In addition to Russian President Vladimir Putin, Armenian Prime Minister Nikol Pashinyan invited French President Emmanuel Macron and United States Secretary of State Anthony Blinken to discuss the situation. Blinken urged an immediate end to the hostilities that each side has blamed on the other. read more “Many positions, shelters and fortified points of the armed forces of Azerbaijan … were subjected to intense shelling by weapons of various calibers, including mortars, by units of the Armenian army,” the agency said, citing a statement by the Azerbaijani Defense Ministry. “As a result, there are casualties in personnel and damage to military infrastructure.” Azerbaijan’s statements said Armenian forces had engaged in intelligence activities on its border, transported weapons into the region and on Monday night had carried out mining operations. He said its actions were “strictly local in nature aimed at military targets”. Armenia’s Defense Ministry said: “Intensive firing continues – it started as a result of a major provocation by Azerbaijan. The armed forces of Armenia launched a corresponding response.” The conflict first erupted in the late 1980s, when both sides were under Soviet rule and Armenian forces seized swathes of territory near Nagorno-Karabakh—long recognized internationally as Azerbaijani territory but with a large Armenian population. Azerbaijan regained these territories in the 2020 fighting, which ended with a Russian-brokered truce and thousands of residents returning to homes they had fled. The leaders of both countries have since met several times to conclude a treaty aimed at establishing a lasting peace. Sign up now for FREE unlimited access to Reuters.comSign up Report from Reuters. Editing by Ron Popeski, Chris Reese and Sam Holmes Our Standards: The Thomson Reuters Trust Principles.