The US government suggests that Russia is moving to procure weapons from Iran and North Korea as it suffers serious losses of military equipment and personnel in its invasion of Ukraine.
Ukrainian forces are continuing their counteroffensives in the southern areas, including the Kherson region. The military says its troops have retaken a number of settlements in the country's south and in the east.
The British Defense Ministry said on Tuesday that the number of reported sorties by Russian unmanned aircraft in the southern Kherson region was far fewer than in August.
The ministry cited shortages of drone components caused by international sanctions as the reason. They added the shortages were hampering Russian military operations.
The US government, meanwhile, expressed concerns that Iran is working to provide Russia with hundreds of drones.
A senior White House official also said on Tuesday that Russia is trying to buy millions of artillery shells and rockets from North Korea for the war in Ukraine.
The official said that it shows Russia is suffering from shortages of weapons.
On Tuesday, Russia's defense ministry announced that its cruise missiles hit a fuel depot in Dnipropetrovsk in Ukraine's east.
Kremlin spokesperson Dmitry Peskov told reporters that Russian President Vladimir Putin would instruct the government to establish labor guarantees for citizens who wish to volunteer to participate in Russia's so-called "special military operation in Ukraine."
The US-based think tank, Institute for the Study of War, is pointing out that the Russian Presidential Office has begun to secure volunteers as Russia suffers from serious losses of personnel.