CNN  — 

Multiple attacks targeting Russian military infrastructure this week have focused attention on Ukraine’s efforts to develop longer-range combat drones.

The Russian Defense Ministry says the strikes on two air bases Monday – followed by an attack on an air field Tuesday – were carried out by Ukrainian drones, which it claims were brought down by Russian air defenses. Imagery, both satellite and photographs, indicates some damage was done to Russian military planes at one base in Ryazan region.

The Ukrainian Defense Ministry has offered no official comment on the explosions, and the Ukrainian government has not acknowledged adding long-range attack drones to its arsenal. However, a top Ukrainian official has tweeted a cryptic message hinting at the possibility that Kyiv was indeed behind the attacks.

“The Earth is round – discovery made by Galileo. Astronomy was not studied in Kremlin, giving preference to court astrologers. If it was, they would know: if something is launched into other countries’ airspace, sooner or later unknown flying objects will return to departure point,” Ukrainian presidential adviser Mykhailo Podolyak posted.

State-owned weapons manufacturer Ukroboronprom has indicated several times in the last few weeks that it is close to finishing work on a new long-range drone.

In October, it posted on Facebook – along with an image of what appeared to be part of the drone’s structure: “Range is 1000 km (621 miles), weight of the combat unit is 75 kg (165 pounds). Putting the final touches on this one.”

A month later, on November 24, Ukroboronprom published another post: “The next stage of UAV testing – On behalf of the Chief of the General Staff, we are getting ready for flight tests under the action of electronic warfare.”

“Weather, on the one hand, becomes a problem, and on the other hand it’s an additional test for the complex. A kind of crash test.”

A photo showed the words “az vozdam” inscribed on what was purported to be the drone – meaning “I will repay.”

And on Saturday, company spokeswoman Natalia Sad was reported by news agency Ukrinform to have told Ukrainian television that “a number of stages of successful tests have been completed.”

“In accordance with the instructions of the Chief of the General Staff of the Armed Forces of Ukraine, we are moving to the stage of tests involving an e-warfare jamming environment,” she added.

However, there is no public indication that the drone in question has been readied for deployment or was involved in explosions inside Russia.

On Tuesday morning, a drone strike occurred at an air field in Russia’s Kursk region, which borders Ukraine, according to the regional governor.

“As a result of a drone attack, an oil tanker caught fire near Kursk airfield. There were no casualties. The fire is being loca