The Soviet Union never developed or maintained a fleet of true, long range strategic bombers during the second world war. Most of what they did develop in terms of bomber technology was designed to support front line troops and engagements through dive bombing or heavy ordinance. bombers like the PE2, B25, A20, Yer2, IL4, and others were not particularly suited for long range attacks on strategic or civilian targets (although B25's I believe were a part of dolittle raid on Tokyo). In terms of attack aircraft most of the soviet war production geared towards aircraft was focused on the venerable Ilyushin IL2 Sturmovick fighter which Stalin considered so important to the Soviet air effort he is reported as warning -

"Our Red Army now needs IL-2 aircraft like the air it breathes, like the bread it eats. - This is my final warning."

to a government aircraft factory that produced insufficient quantities of the ground attack aircraft. It was armed with 2x 7.62 machine guns, 2x 23mm cannons, and could be armed with a quantity of bombs and rockets. It had a incredibly well armored fuselage protecting the pilot and eventual rear gunner (the original models lacked a rear gunner making them incredibly vulnerable to enemy fighters) from amounts of flak that would have destroyed almost any other allied aircraft. But with the added armor protection came vulnerability - since the aircraft was relatively slow and the top of the aircraft wasn't particularly well protected, thousands would be shot down over the course of the war. They would constantly harass ground targets and troop formations by either flying in formations resembling British and American bomber groups or fly just above the ground on the prowl to smash targets of opportunity.

Even though production in terms of bombers or attackers was directed mostly towards the IL2 Sturmovick fighter, the soviets did mount a daring and extremely dangerous air raid on berlin that did little to no damage in mid 1941 with IL4 bombers and others stationed from an Island in the Baltic, off the Estonian coast. Earlier soviet bombers had attacked Finnish cities in the beginning of and during the course of the Winter War in 1939-1940 that destroyed portions of major cities like Helsinki. Early on in the course of the war the Soviet foreign minister Vyacheslav Molotov denied that Soviet bombers were dropping cluster bombs on civilians insisting that it was Soviet aircraft dropping food supplies to starving Finnish citizens. The Finns at the time were most definitely not starving or in need of aid, persuading the Finns to nickname the bombs "Molotov Bread Baskets". This was one of the first instances of bombing raids directed against civilians by the Soviets during the course of World War II.

But the Soviets again never developed strategic bombers as a part of their air force strategies - all resources were devoted to supporting ground operations and harassing German supply lines or formations caught in the open. The Germans too never developed a true strategic bomber in large enough quantities to engage is long range bombing campaigns. Neither the Heinkel He111, Junkers Ju88, Dornier Do217 (the flying pencil), or even the Arado jet bomber in later years (the first such aircraft ever devised) had the range, bombload, or protection to engage in anything reminiscent of Allied campaigns over axis territory. Indeed the Soviets were more than content to let the remaining allied airforces engage in strategic bombing and preserve their own air forces for purely military objectives in support of front line operations

Although towards the end of World War II - the Soviets were able to procure examples of the extremely advanced, American B29 Superfortress after their crews landed on Soviet Airfields following raids on Japan from the Marianas. The B29 was advanced in its extremely long range, massive 18,000lb bomb load, pressurized crew compartment, and computer controlled remote turrets - with multiple stations being able to fire from the command of a single crewman. The Soviets were able to copy this aircraft which spawned the Tuplolev TU-4 heavy bomber which first flew in 1947

While it's true that the Soviet Union during World War II focused mainly on ground attack aircraft, they did maintain a strategic bombing wing named Long Range Aviation.

During the Winter War with Finland (which may or may not be considered as part of World War 2, or a separate conflict) the LRA bombed several Finnish cities including Helsinki, Turku, and Viipuri. While Viipuri was close to the Soviet ground offensive, Helsinki and Turku were not so those bombings were more of a strategic bombing nature.

The most similar operation to the strategic bombing performed by the Western allies was probably the Budapest bombings, which dropped approximately 8,000 tonnes of bombs over four nights in September of 1944.

While the strategic bombing wing did exist and did perform city bombing operations, it does need to be put in context with the western strategic bombing efforts. Soviet strategic bombing in Germany ultimately accounted for less than 1% of total tonnage dropped on Germany during World War II.

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An interesting point of trivia is that the term 'Molotov cocktail' originates from Soviet strategic bombing of the Finnish cities during the winter war. The Soviet Union dropped incendiary cluster bomb munitions on Finnish cities, but the Soviet foreign minister Vyacheslav Molotov claimed that the Soviet Union was only dropping food aid to the Finnish civilians. Those bombs were sarcastically named 'Molotov Bread baskets'. Eventually the Finns named the improvised explosive devices 'Molotov Cocktails' since they were a "drink to go with the food" that the Soviets were claiming to send.