KYIV, Ukraine — Ukraine launched a new phase of its massive anti-corruption campaign on Wednesday, dismissing officials and conducting searches on high-profile targets in an effort to boost public morale and preserve international support for the country, a top presidential adviser announced.

The anti-corruption measures take place two days before Ukraine prepares to host a summit with the European Union in Kyiv, which Ukrainian officials hope will bolster their bid to become a full member of the political and economic bloc.

Ukrainian authorities are investigating current and former top officials in the defense and energy ministries and the tax office, among others, for embezzlement and other illegal activity. The entire management of the country's customs service was dismissed.

"Today's corruption cases against top officials are just the beginning," Oleksiy Sukhachev, director of the State Bureau of Investigation (SBI), said in a news release.

"The time when it was possible to rob the state with impunity and undermine its combat readiness has passed and passed a long time ago," he added.

President Volodymyr Zelensky forecast the measures, which included the property search of a major oligarch, in his nightly speech Tuesday, saying officials were "preparing new reforms" that would "change the social, legal and political reality in many ways, making it more human, transparent and effective."

The 27-member bloc is broadly supportive of Ukraine, but it is divided on just how fast the war-torn, impoverished country will join its club and has set forth bureaucratic measures, including an effort to root out official corruption, as conditions of joining.

Mykhailo Podolyak, a top adviser to Zelensky, said in an interview that the flurry of anti-corruption activity last week and Wednesday was part of a major housecleaning effort.

Last week, there were 10 high-level dismissals, which included Zelensky's deputy chief of staff, a deputy defense minister, deputy prosecutor general and a number of prominent heads of regional administration.

At the time, officials described those firings as just the beginning of a response to long-standing internal complaints about corruption. They were also probably in response to concerns of the Republican Party, which recently took control of the U.S. House and has raised questions about the scope of U.S. aid to Ukraine.

"It is clearly a signal of their determination and of the functioning of what they have now put in place," said an E.U. official on Wednesday about the earlier dismissals, speaking on the condition of anonymity to brief the press.

Podolyak said some officials had "lost the feeling that the war imposes increased requirements of transparency" and continued to grow rich at the public's expense. Zelensky launched investigations of top officials suspected of corruption, and the results are now being seen, with more to come, he said.

Ukraine's security service, the SBU, said in a news release Wednesday that it was "conducting a series of large-scale operational and investigative measures aimed at fighting the internal enemy," which included dozens of searches across the country.

Although the latest measures weren't directly connected to Friday's E.U. summit, Podolyak said, the anti-corruption drive was launched in part because Ukraine's Western partners "provide significant financial, military and resource assistance" and could ask questions "that will lead to the assistance being partially suspended."

"We are taking advantage of this moment when, on the one hand, we have a war, and on the other hand, we are engaged in solving the problem of advancing to the European Union," he said.

He conceded that Ukraine's admission of having a corruption problem risked bolstering arguments against Ukraine and providing fuel to the Russian propaganda machine.

"The president is saying publicly: 'Look, I want to be honest. I want a transparent state behind me, so that you can trust us,'" Podolyak said.

Last week's dismissals appeared to be connected to recent allegations of corruption revealed by the media, including an investigation into inflated prices in a food procurement contract for the Defense Ministry.

Details of the latest moves emerged Wednesday when David Arakhamia, leader of Zelensky's party in parliament and a close adviser to the president, said on his Telegram channel that properties belonging to billionaire Ihor Kolomoisky and former interior minister Arsen Avakov had been searched.

Kolomoisky, among the richest people in Ukraine, has been enmeshed in financial scandals. He is under investigation in the United States for alleged corruption and money laundering. He was once seen as being close to Zelensky and a key supporter of his presidential bid in 2019.

Arakhamia also said that "notes of suspicion," indicating the opening of investigations, had been delivered to top officials in the country's Defense Ministry.

Ukraine "will change during the war," Arakhamia said. "If someone is not ready for change, then the state itself will come and help them change."

The government is investigating a former deputy defense minister, identified in the Ukrainian media as Vyacheslav Shapovalov, for embezzlement, saying he lobbied for contracts to purchase supplies for the military at inflated prices. He allegedly bought low-quality bulletproof vests, helmets and other items for a sum of more than $27 million. Shapovalov resigned his post last week in connection with a food procurement scandal uncovered by Ukrainian media outlets.

Investigators also accused the head of Kyiv's tax inspectorate of embezzling millions of dollars and leading a highflying life inconsistent with her official income level. And they reported the former minister who oversaw Ukraine's energy and coal industry for official negligence leading to budget losses of nearly $41 million, in an arrangement that benefited a major gas oligarch.

The SBU said it had searched properties associated with construction companies in Kyiv accused of "illegal schemes" to launder funds to advance the interests of former lawmakers Viktor Medvedchuk and Taras Kozak. Medvedchuk, a close ally of Russian President Vladimir Putin, was under house arrest in Ukraine before authorities released him to Russia in a prisoner swap in September.

Avakov, whose premises were searched, acknowledged the investigation in a statement Wednesday and said it was in connection with a recent helicopter crash in Kyiv.

The crash killed Interior Minister Denys Monastyrsky and other top officials. Avakov said officials from Ukraine's State Security Service and State Bureau of Investigation were interested in details of the purchase of the Airbus Super Puma helicopters, which were involved in the crash.

"Naturally, they found nothing related to the interests of the investigation," he said.

The Washington Post’s Emily Rauhala in Brussels contributed to this report.