Russia has sent a military convoy through Ukraine's border, a paramilitary group within the Ukrainian army said Monday.Ukrainian National Guard's volunteer unit Azov Battalion claimed in a statement that 30 Russian tanks, grad rockets and howitzers were moving towards Novoazovsk and Mariupol, which fall within the so-called "Donetsk People's Republic" run by pro-Russian separatists in the restive east.The battalion said some vehicles in the convoy trying to enter from Russia had been stopped in border.It added the Ukrainian army did not have enough troops in Mariupol for a possible confrontation.Chairman of the Kiev-based Center of Military-Political Research, Dmitry Tymchuk, confirmed Monday that a Russian military convoy entered Ukraine in Novoazovsk, but that a major part of it was halted on the border by Ukrainian armed forces using gunfire.Ukraine launched its 'anti-terror operation' in mid-April to restore control over the regions of Donetsk and Luhansk where pro-Russian separatists declared independence from the Kiev administration.