Russian President Vladimir Putin has ordered the country's military to increase its number of troops by 180,000 to a total of 1.5 million, as Moscow's military action in Ukraine drags on for more than two-and-a-half years.

The move comes after Ukraine's intelligence chief claimed Russia was looking to complete the war by 2026. 

Mr Putin's decree, published on the official government website, will take effect on December 1. 

It sets the overall number of Russian military personnel at nearly 2.4 million, including 1.5 million troops, and orders the government to provide the necessary funding.

The previous increase in Russian troop numbers came last December, when a decree by Mr Putin set the total number of Russian military personnel at about 2.2 million, including 1.32 million troops. 

The most capable Russian troops have been pressing an offensive in eastern Ukraine, where they have made incremental but steady gains in the past few months. 

In June, Mr Putin put the number of troops involved in what the Kremlin calls the "special military operation" in Ukraine at nearly 700,000. 

A recent update from UK Defence Intelligence said Russian casualties were averaging more than 1,000 per day, killed and wounded. 

The British and Ukrainian governments both estimate Russia has suffered more than 600,000 casualties since the 2022 invasion. 

Russia has relied on volunteers since unpopular mobilisation

After calling up 300,000 reservists in the face of Ukraine's counteroffensive in the fall of 2022, Russian authorities have switched to filling the ranks of troops fighting in Ukraine with volunteer soldiers, who have been attracted by relatively high wages.

Many commentators have noted that the Kremlin has been reluctant to call more reservists, fearing domestic destabilisation like what happened in 2022 when hundreds of thousands fled Russia to avoid being sent to combat.

The shortage of military personnel has been widely cited as a key reason behind the success of Ukraine's incursion into Russia's Kursk region launched on August 6.

The Kremlin has sought to avoid the redeployment of troops from eastern Ukraine and relied on reinforcements from other areas to stem the Ukrainian incursion. 

Ukraine predicts 2025 will be pivotal

The recruitment drive comes as Ukraine braces for an expected escalation of hostilities in 2025, with an intelligence chief predicting Russia wants to wind up the war by 2026.

Lieutenant General Kyrylo Budanov, chief of the Defence Intelligence of Ukraine, said Russia would face a worsening economic and social climate by mid-2025, along with increasing difficulty recruiting troops.

"These are Russia's calculations. If they do not come out of this war as self-professed winners by this time, then in the near future, about 30 years, they will lose the opportunity to be a superpower," he told the Yalta European Strategy meeting in Kyiv. 

US defence think tank the Institute for the Study of War said Russia would likely become increasingly reliant on foreign partners to meet its needs.

In its September 15 assessment, it said Russia had relied on refurbishing stocks of Soviet-era weapons and equipment, particularly armoured vehicles, in Ukraine.

"It is unclear if the Russian defence industry will be able to produce enough to sustain the high level of equipment losses that Russian forces suffer in Ukraine even with further economic mobilisation," it said.

The Russian defence ministry on Monday reported reclaiming control of two more villages in the Kursk region from Ukrainian forces.

ABC/AP