Ukrainian authorities say an attack has damaged Russia's most advanced Sukhoi Su-57 fighter jet at an airfield in southern Russia.

Ukraine's intelligence service released a report on Sunday saying it was the first time an Su-57 stealth jet had been damaged. The aircraft was parked at an airfield in the Astrakhan region of Russia, about 590 kilometers away from the frontlines of the conflict in Ukraine.

The report included satellite images of the Su-57 on the base taken on Friday and Saturday. It says the aircraft was intact in the image on Friday but the one taken the following day shows distinct explosion marks around the fighters. It did not mention the extent of the damage.

Astrakhan's governor in a social media post on Saturday blamed a Ukrainian military drone for the attack, saying the drone was shot down. There was no mention about the damage.

On Sunday, British Sky News television quoted Ukrainian military sources as saying a warplane for the first time has struck a target in Russia's Belgorod, neighboring the eastern Ukrainian region of Kharkiv.

The network said it was not immediately clear whether a Western weapon was used in the attack.

Washington gave permission for Ukraine to use US-provided weapons to strike targets in Russia to help with the defense of Kharkiv.