The shock Ukrainian invasion of Kursk has the Kremlin pulling some troops out of Ukraine to defend Russia, per reports

• Ukraine launched a shock counter-invasion into Russia last week.
• US officials told the Wall Street Journal that Russia is withdrawing troops from Ukraine in response.

Russia is withdrawing some of its troops from Ukraine in response to Ukraine's counter-invasion into Russia that started last week, the Wall Street Journal reported on Tuesday, citing unnamed US officials.

Politico Europe also reported on Tuesday that an official in Kyiv said a "relatively small" number of Russian units were withdrawn to respond to the incursion in Kursk. US officials told the Journal it was still unclear how many troops Russia was pulling back from Ukraine.

The State Department and the White House did not respond to requests for comment from Business Insider.

Ukraine pulled off a shock incursion into Russia starting around August 6, sending troops into the Kursk region. Kyiv this week said Ukrainian forces had taken nearly 400 square miles of Russian territory in a matter of days — that's almost as much as Russia has taken in Ukraine this year. Business Insider could not independently verify how much territory had been taken by Ukraine.

Ukraine has not said much about the incursion. In an address on Monday, Ukraine President Volodymyr Zelenskyy said Russian shells were being fired at Ukraine from the Kursk region and called the operation a "security matter," according to Politico Europe.

''It is only fair to destroy Russian terrorists where they are, where they launch their strikes from," Zelenskyy said. He also said Ukraine would be able to build up its prisoner-of-war "exchange fund."

The ultimate end goal has not been clear, though military analysts have said Kyiv could be trying to gain negotiation leverage or provide relief to its troops elsewhere by straining Russia's resources, BI previously reported.

Ukraine could also have been trying to embarrass Russia. Though the Kremlin tried to downplay the attack, military analysts previously told BI's Tom Porter that the attack puts a dent in Putin's strongman image.

Putin has even sought to blame the West for the attack and said that Russia's "peaceful" people do not deserve to be invaded.

The US had a simple response, with John Kirby, the White House national security communications advisor, saying on Monday: "There's an easy solution: He can just get the hell out of Ukraine and call it a day."

Heorhiy Tykhi, a spokesman for the Ukrainian foreign ministry, has said the purpose of the attack is to "save the lives of our people and protect the territory of Ukraine from Russian attacks," the Journal reported.

"The sooner the Russian Federation agrees to restore a just peace…the sooner the raids of the Ukrainian defense forces on the territory of the Russian Federation will stop," he added.