One of Ukraine's main goals in invading Russia appears to be working

• Russia is pulling some troops from the front line in Ukraine, reports said.
• They're being redeployed to fight the Ukrainian incursion in Kursk.
• Analysts say a major Ukrainian aim is to ease pressure on the front line.

Russia is pulling troops from its invasion force in Ukraine to help defend against Kyiv's audacious attack on Russian territory, according to reports.

Ukraine's invasion of the province of Kursk last week took Russia by surprise. Its troops are now believed to be in control of around 28 Russian towns and villages and about 300 square miles of territory.

Analysts told Business Insider that one of Ukraine's core aims in the operation is to divert Russian troops from the front line in Ukraine.

According to a Ukrainian official, there is evidence it's happening.

"Russia has relocated some of its units from both Zaporizhzhia and Kherson regions of Ukraine's south," Dmytro Lykhoviy, a Ukrainian army spokesman, told POLITICO Tuesday.

Lykhoviy said that the number of Russian troops being diverted is "relatively small," but there's evidence that Russia's moving troops from other parts of Ukraine as well, with no sign of Ukraine's attack in Kursk easing off.

The Institute for the Study of War (ISW), a US think tank, said Tuesday that according to Russian military bloggers, Russia has yet to stabilize the situation in Kursk a week into the attack and Ukrainian units are continuing to make advances.

On Wednesday, Ukraine's general staff said his soldiers had shot down a $36 million Russian Su-34 bomber jet "during a combat mission" in the Kursk region.

It's the first time since World War II a foreign military has occupied Russian territory.

The ISW cited Russian sources saying that some Russian irregular units had also been pulled from Donetsk in east Ukraine, which has been the scene of intense fighting and where Russia has made incremental gains.

It said that Russia could be diverting troops from units in Donetsk intended to relieve or reinforce front-line units.

These units appeared to be relying on "Russian conscripts, and elements of some regular and irregular military units pulled from less critical sectors of the frontline to address the ongoing Ukrainian incursion."

"Russian military command has determined that possible disruptions to the offensive operations in northern Kharkiv Oblast and other less-critical frontline areas are an acceptable risk to adequately respond to the Ukrainian incursion in Kursk Oblast," it continued.

And Laurynas Kasčiūnas, Lithuania's defense minister, in a meeting with Ukraine's President Volodymyr Zelesnkyy on Tuesday said Russia was also sending troops from its Baltic enclave Kaliningrad to Kursk.

BI has been unable to confirm reports of the redeployments, and it is unknown exactly how many Russian troops may have been diverted to fight Ukraine's Kursk incursion.

According to reports, Russia's response has been hampered by unclear chains of command and inexperienced troops defending the territory attacked by Ukraine.

For months, Ukraine's forces have been losing ground to Russia in a grinding war of attrition. The Kursk assault has changed the dynamic of the conflict, putting Russia on the back foot.

But it's unclear how long Ukraine can sustain the momentum of the attack given problems with troop shortages, and how many resources it will put into defending the territory seized in Russia.