Rescuers searched for survivors in the rubble of an apartment building in eastern Ukraine on Thursday after a Russian strike destroyed it, as Kyiv said it expected a major offensive on the first anniversary of Moscow's invasion. At least three people were killed Wednesday and 20 wounded when a Russian rocket struck a residential building in the center of Kramatorsk, located in Ukraine's eastern industrial region of Donetsk. Rescuers wearing torches on their heads worked to pull survivors from the debris, their faces covered in dust as they tried to find any signs of life under the cover of night. After discovering the body of a resident who was crushed under the rubble, rescuers carried the victim away on a stretcher, as firefighters worked their way through the mangled building structure. Donetsk regional police said paramedics, search-and-rescue dogs, and explosive experts were combing the area as they believed that more people could be trapped. "I first heard a whistle and then everything started to fly around," said Petro, 71, whose apartment was damaged. "Peaceful people died and are under the rubble," Ukrainian President Volodymyr Zelensky wrote after the rocket strike. "This is the daily reality of life in our country." The strike in Donetsk -- where Moscow has claimed to have captured fresh ground recently -- came as the first anniversary of Russia's invasion of Ukraine approached. "Given that (the Russians) live through symbols, we think that they will try something around February 24," Ukrainian Defense Minister Oleksiy Reznikov said during an interview with French television, broadcast late Wednesday. "They could try an offensive on two fronts... We need arms to counter the enemy," he said. "We do not underestimate our enemy... Their mobilization has not stopped," he said. Reznikov said Kyiv believes Moscow has deployed about half a million troops -- far more than Russia's claim of 300,000 personnel currently mobilized. - Anti-corruption drive - Ukraine expanded a clampdown on corruption Wednesday, launching coordinated searches of residences linked to a divisive oligarch and former interior minister as well as tax offices in the capital. The searches came ahead of a key summit with the European Union and appeared to be part of a push by Kyiv to reassure military and financial donors in European capitals and Washington that Ukraine is tackling systemic graft. "We are carrying out the task set by Ukrainian President Volodymyr Zelensky and simultaneously delivering a global blow to the internal enemy," announced Vasyl Maliuk, the head of Ukraine's security service, the SBU. "Every criminal who has the audacity to harm Ukraine, especially in the conditions of war, must clearly understand that we will put handcuffs on him." The searches have targeted influential billionaire Igor Kolomoisky and former interior minister Arsen Avakov, said the head of Zelensky's party David Arakhamia. Law enforcement also raided tax offices in the capital and senior customs officials were fired, Arakhamia said. Ukraine has suffered from corruption for years, but efforts to stamp it out have been overshadowed by Moscow's invasion last February. In the biggest political shakeup since the launch of Moscow's assault on Ukraine, authorities last week fired around a dozen senior figures, including defense officials and a top aide to the president's office. Wednesday's raids came two days before Zelensky was expected to host a summit with the EU, which has urged reforms to facilitate deeper integration. - 'All necessary steps' - Investigators from the SBU released images of a search from the home of Kolomoisky, who was barred from entering the United States over allegations of corruption and undermining democracy. Prior to the invasion, Kolomoisky was one of the country's richest men, with holdings in a slew of industries, including media, aviation and energy. The security service said the search had been launched over an investigation into the embezzlement of 40 billion hryvnia (about $1.1 billion) from energy holdings. The government seized stakes in the energy companies -- oil producer Ukrnafta and refiner Ukrtatnafta -- as part of moves to consolidate the war effort. The SBU also said it had uncovered a scheme by the head of the Kyiv tax office involving "multimillion-dollar" fraud schemes. They accuse the official of having abused a position of authority. The State Bureau of Investigation and the Prosecutor General's Office said Wednesday they had informed several senior officials they were under investigation for crimes including misappropriation of state funds and misuse of state property. - Crossing the line - In the past week, Western powers including US and Germany have approved sending more than 100 battle tanks to Ukraine -- a move that Russia has warned crosses a dangerous new line in the conflict. Zelensky is now working to drum up political backing for Ukraine at a critical time in the conflict, calling on the West to supply fighter jets and long-range artillery. The Kremlin said Wednesday that any deliveries of long-range weapons to Ukraine would not alter Russia's military objectives or change its strategy on the battlefield. "It would require greater efforts from us. But again, it won't change the course of events," Kremlin spokesman Dmitry Peskov told journalists.