Nato is monitoring closely increasing Russian troop numbers stationed near the Ukrainian border, alliance chief Jens Stoltenberg said on Monday. “In recent weeks, we have seen large and unusual concentrations of Russian forces close to Ukraine’s borders,” Stoltenberg said at a press conference in Brussels alongside Ukrainian Foreign Minister Dmytro Kuleba. Any further provocation or aggressive actions by Russia would be of serious concern, Stoltenberg said, adding that Nato is monitoring the situation “very closely”. Kuleba said what was important now was that there was close coordination to deter Russia. Whatever the price of deterrence, the price of a new conflict will be higher, he said. Since 2014, parts of the eastern Ukrainian regions of Luhansk and Donetsk – known collectively as Donbass – have been controlled by Russian-backed separatists. Moscow has fended off accusations about a build-up in recent weeks, saying it can move troops on its own territory as it pleases.