"We have said on many occasions that no weapon is supplied there," Xinhua quoted Kremlin spokesperson Dmitry Peskov as saying in a radio interview.
Aleksandr Zakharchenko, prime minister of the self-declared Donetsk People's Republic (DPR), said at a meeting that the militia had received some 150 combat vehicles, including 30 tanks.
Zakharchenko said their units had been reinforced by 1,200 fighters "who have received four months of training on Russian territory".
Western countries have been accusing Russia of arming the insurgents in Ukraine since the outbreak of the crisis, while Kiev has repeatedly blamed Moscow for inciting the separatist unrest in eastern Ukraine.
The humanitarian aid convoy dispatched by Moscow also sparked speculations that Russia could use it as a cover for weapon transfer to the insurgents.