Russia has stepped up its military assistance to Syria, including armored vehicles and drones and precision-guided bombs, informed sources told Reuters news agency.
A number of sources told Reuters that Assad forces received since December arms and military supplies including drones, which Russia arranged to deliver to Syria whether directly or through agents.
"Dozens of Antonov 124s (Russian transport planes) have been bringing in armoured vehicles, surveillance equipment, radars, electronic warfare systems, spare parts for helicopters, and various weapons including guided bombs for planes," a Middle East security source said.
"Russian advisers and intelligence experts have been running observation UAVs around the clock to help Syrian forces track rebel positions, analyse their capabilities, and carry out precision artillery and air force strikes against them," said the source, who declined to be identified.
A source within the international arms industry with knowledge of Middle Eastern weapons movements also confirmed a pick-up in supplies to Assad's forces, including UAVs.
"Equipment has been moving into Syria, and Russia is either bringing it in themselves or sourcing supplies from Black Sea areas like Bulgaria, Romania or Ukraine, where there is surplus stock floating around," the source said. "Suppliers in that region cannot afford to upset the Russians."