Russia has developed and started deploying a "more dangerous" subsonic missile to bring down Ukraine's energy grid, a US-based think tank has claimed.

       The Institute for the Study of War (ISW) claimed Vladimir Putin's army has now turned to the slower Kh-69 cruise missile to bombard Kyiv's infrastructure.

       The ISW said evidence suggested the Kh-69 has already been used in strikes that destroyed a large section of the Trypilska Thermal Power Plant (TPP) in Kyiv Oblast last week.

       The subsonic air-to-surface missile is believed to be slower than the air-launched Kh-47M2 Kinzhal – Russian for 'dagger' – but Ukraine's military experts have warned the new model "in terms of its consequences for Ukrainians, may be more dangerous."

       According to Defense Express, the Kh-69 has a smaller warhead and does not reach the speed of its hypersonic counterpart but "the use of the Kh-69 missile may be considered a worse option for Ukraine."

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       The ISW noted the latest reports show the subsonic cruise missile can be launched up to 240 miles away from the target – 50 miles over initial estimates.

       Ukrainian Air Force spokesperson Major Ilya Yevlash said the Kh-69 is an improved version of the Kh-59 model Moscow has been using so far to target Ukraine's energy infrastructure.

       While conceding the subsonic missile can be more dangerous to Ukraine, he also noted the manufacturing process heavily relies on Russia's ability to source critical components.

       Major Yevlash suggested Moscow's scope for producing a large stock of Kh-69 quickly was small considering reported issues plaguing Putin's military supply chain.

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       The deployment of the Kh-69 comes as Ukraine's military chief warned that the battlefield situation in the industrial east has "significantly worsened in recent days."

       Gen. Oleksandr Syrskyy said that Moscow had “significantly” ramped up its assaults since Putin extended his nearly quarter-century rule in a preordained election last month.

       According to Syrskyy, Russian forces have been “actively attacking” Ukrainian positions in three areas of the eastern Donetsk region, near the cities of Lyman, Bakhmut and Pokrovsk.

       Russian forces also began to launch tank assaults as drier, warmer spring weather has made it easier for heavy vehicles to move across previously muddy terrain.