MOSCOW Russian President Vladimir Putin said on Monday that the army would eject Ukrainian troops from Russian sovereign territory after Kyiv's biggest incursion across the border since the start of the war in 2022.

Ukrainian forces rammed through the Russian border last Tuesday and swept across some western parts of Russia's Kursk region, a surprise attack that may be aimed at gaining leverage in possible ceasefire talks after the US election in November.

Apparently caught by surprise, Russia by Sunday had stabilised the front in the Kursk region, though Ukraine had carved out a sliver of Russian territory where battles were continuing on Monday, according to Russian war bloggers.

In the neighbouring Belgorod region to the south, regional governor Vyacheslav Gladkov said evacuations of civilians had begun from the Krasnaya Yaruga District due to "enemy activity on the border".

Putin, in his most detailed remarks on the incursion to date, said that Ukraine "with the help of his Western masters" was trying to improve its negotiating position ahead of possible ceasefire talks and to undermine Russian advances.

Putin told security officials and regional governors that the Ukrainian forces were suffering heavy casualties in their incursion.

"The enemy will certainly receive a worthy response, and all the goals facing us will, without a doubt, be achieved."

Putin said Ukraine was trying to intimidate Russian society and thus undermine stability. He warned senior officials that Ukraine would seek to further destabilise border regions.

At the Putin meeting, the acting governor of Kursk, Alexei Smirnov, said Ukraine controlled 22 settlements in the region, and that the incursion was about 12 km deep and 40 km wide.

Russia has imposed tight security in the Kursk, Bryansk and Belgorod regions while its ally Belarus said it was bolstering its troop numbers at its border after Minsk said Ukraine had violated its airspace with drones.

Russian officials say Ukraine's attacks on Russian territory are aimed at showing its Western supporters that Kyiv can still muster major military operations while trying to gain a bargaining chip ahead of possible ceasefire talks.

Russia invaded Ukraine in February 2022 and now controls 18% of Ukrainian territory. Russian forces, which have a vast numerical supremacy, have been advancing this year along the 1,000-km (620-mile) front after the failure of Ukraine's 2023 counteroffensive to make any major gains.

Kyiv broke its silence on the attacks on Saturday when President Volodymyr Zelenskiy said Ukraine had launched an incursion into Russian territory to "restore justice" and pressure Moscow's forces.

At the Zaporizhzhia nuclear power plant, in a part of Ukraine controlled by Russian forces, a major fire broke out.

The Ukrainian attack has prompted some in Moscow to question why Ukraine was able to pierce the Kursk region so easily after more than two years of the most intense land war in Europe since World War Two.

Russian war bloggers said Ukrainian forces in Kursk were trying to encircle Sudzha, where Russian natural gas flows into Ukraine, while major battles were underway near Korenevo, about 22 km (14 miles) from the border, and Martynovka.

"The situation on the borders of the western Belgorod region is alarming," said Yuri Podolyaka, an influential pro-Russian military blogger, adding that Ukraine was probing the border at several places.

"The enemy has three fairly large groupings here."

Since the Aug 6 border incursion into Kursk, the Russian rouble has weakened, losing 6% of its value against the US dollar. Russia's Gazprom said it would send 39.6 million cubic metres (mcm) of gas to Europe via Ukraine on Monday.

Though the United States said it had not been told of the Ukrainian operation before it was unleashed, there were signs in Moscow that the attack would provoke a response from Russia.

"We have no doubt that the organisers and perpetrators of these crimes, including their foreign curators, will bear responsibility for them," said Maria Zakharova, spokeswoman for the Russian Foreign Ministry.

"A tough response from the Russian Armed Forces will not take long."

  - Reuters