Armenia and Azerbaijan reported fresh border clashes that left an unknown number of Azerbaijani soldiers dead. The fighting, which broke out early on Tuesday, marks the latest flare-up between the foes, who fought in 2020 over the disputed Nagorno-Karabakh region. Each side blamed the other for the battle. In a statement, Armenia’s defense ministry said Azerbaijan launched “intense shelling” against Armenian army positions in the direction of the cities of Goris, Sok and Jermuk at 00:05 am. (20:05 GMT) on Tuesday. Azerbaijani troops used drones, as well as “artillery and large-caliber firearms,” it said. “The armed forces of Armenia have launched a corresponding response,” it added. But Azerbaijan’s defense ministry accused Armenia of “large-scale subversive actions” near the border districts of Dashkesan, Kelbajar and Lachin, adding that its army positions “came under fire, including from trench mortars.” “There are losses between [Azerbaijani] soldiers,” he said, without giving details. The United States said it was deeply concerned by reports of the attacks. “As we have long made clear, there can be no military solution to the conflict,” US Secretary of State Anthony Blinken said on Monday. “We call for an immediate end to military hostilities.” There have been frequent reports of fighting along the Armenia-Azerbaijani border since the end of their war in 2020. Last week, Armenia accused Azerbaijan of killing one of its soldiers in a border attack. In August, Azerbaijan said it lost one soldier and the Karabakh military said two of its troops were killed and more than a dozen wounded. The neighbors have fought two wars over the Nagorno-Karabakh region, the Armenian enclave in Azerbaijan. The conflict first erupted in the late 1980s, when both sides were under Soviet rule and Armenian forces seized swaths of territory near Nagorno-Karabakh — long recognized internationally as Azerbaijani territory but with a large Armenian population. About 30,000 people died in the ensuing conflict. 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. More than 6,500 people lost their lives in the six-week war. The leaders of both countries have since met several times to conclude a treaty aimed at establishing a lasting peace. During EU-brokered talks in Brussels in May and April, Azerbaijani President Ilham Aliyev and Armenian Prime Minister Nikol Pashinyan agreed to “advance discussions” on a future peace treaty. Pashinyan on Tuesday had separate phone calls with Russian President Vladimir Putin and French President Emmanuel Macron about the latest clashes, according to Armenia’s government. The prime minister condemned the “provocative, aggressive actions” of Azerbaijan’s armed forces and called for an “adequate response from the international community,” Armenia’s government said.