According to military strategists, a two-day assault from Ukraine into Russia’s western borders may compel the Kremlin to shift soldiers from the front lines while Kyiv prepares a massive counteroffensive, as well as give Moscow a psychological hit.

Though Kyiv has denied any involvement, analysts say the greatest cross-border attack from Ukraine since Russia invaded 15 months ago was almost probably organized with Ukraine’s military forces as it prepared to recover territory.

“The Ukrainians are trying to pull the Russians in different directions to open up gaps. The Russians are forced to send reinforcements,” said Neil Melvin, an analyst at the Royal United Services Institute (RUSI).

Ukraine says it plans to conduct a major counteroffensive to seize back occupied territory, but Russia has built sprawling fortifications in its neighbor’s east and south in readiness.

The incursion took place far from the epicenter of fighting in Ukraine’s eastern Donbas region and around 100 miles (160 km) from the front lines in the northern Kharkiv region.

“They’ll have to respond to this and put troops there and then have lots of troops all along the border area, even though that may not be the way the Ukrainians are coming,” Melvin said.

Russia’s military said on Tuesday it had routed militants who attacked its western Belgorod region with armoured vehicles the previous day, killing more than 70 “Ukrainian nationalists” and pushing the remainder back into Ukraine.

Kyiv has said the attack was carried out by Russian citizens, casting it as homegrown, internal Russian strife. Two groups operating in Ukraine – the Russian Volunteer Corps (RVC) and Freedom of Russia Legion – have claimed responsibility.

The groups were set up during Russia’s full-scale invasion and attracted Russian volunteer fighters wanting to fight against their own country alongside Ukraine and topple President Vladimir Putin.

Mark Galeotti, head of the London-based Mayak Intelligence consultancy and author of several books on the Russian military, said the two groups comprised anti-Kremlin Russians ranging from liberals and anarchists to neo-Nazis.

“They’re hoping that in some small way they can contribute to the downfall of the Putin regime. But at the same time, we have to realise that these are not independent forces … They are controlled by Ukrainian military intelligence,” he said.

Ukrainian presidential aide Mykhailo Podolyak repeated Kyiv’s position that it had nothing to do with the operation.

The United States says it does not “enable or encourage” Ukrainian attacks on Russian territory, but that it is up to Kyiv to decide how it conducts military operations.

Several similar incursions into Russia have occurred in recent months, and although this week’s was the largest known so far, it is still tiny when compared to frontline battles.