Russian warplanes were damaged but not destroyed in a June 1 attack by Ukraine, and they will be restored, Russian Deputy Foreign Minister Sergei Ryabkov said.

Ukrainian strikes targeted airfields in Siberia and the far north where Russia houses heavy bombers that form part of its strategic nuclear forces.

The United States assesses that up to 20 warplanes were hit and around 10 were destroyed, two U.S. officials told Reuters, a figure that is about half the number estimated by Ukrainian President Volodymyr Zelenskyy.

But Ryabkov, who oversees arms control diplomacy, told state news agency TASS: "The equipment in question, as was also stated by representatives of the Ministry of Defence, was not destroyed but damaged. It will be restored."

It was not immediately clear how swiftly Russia could repair or replace the damaged aircraft - if at all - given the complexity of the technology, the age of some of the Soviet-era planes, and Western sanctions that restrict Russian imports of sensitive components.

Commercial satellite imagery taken after the Ukrainian drone attack shows what experts told Reuters appear to be damaged Russian Tu-95 strategic bombers and Tu-22 Backfire long-range bombers that Russia has used to launch missile strikes against Ukraine.

Russian President Vladimir Putin told U.S. President Donald Trump in a telephone conversation on Wednesday that Moscow would have to respond to the attacks, Trump said.

Russia has an estimated fleet of 67 strategic bombers, including 52 Tu-95s, known as Bear-H by NATO, and 15 Tu-160s, known as Blackjacks, of which about 58 are thought to be deployed, according to the Bulletin of the Atomic Scientists.

In addition, it has 289 non-strategic fighters and bombers, including Tu-22s, Su-24s, Su-34s and MiG-31s, according to the Bulletin. Russia has given no detail about which aircraft were damaged but said that Ukraine targeted five airbases.