Ukraine on Wednesday expanded a clampdown on corruption with coordinated searches of residences linked to a high-profile oligarch and former interior minister, and tax offices in the capital, a senior official said.

The head of President Volodymyr Zelensky's party, David Arakhamia, said that a house belonging to politically connected oligarch Igor Kolomoisky was searched, alongside that of former interior minister Arsen Avakov.

Tax offices were raided and customs officials were also fired, he said in a post on social media announcing the shake up.

"The country will change during the war. If someone is not ready for change, then the state itself will come and help them change," he added.

Ukraine for years has suffered endemic graft but efforts to stamp it out recently have been overshadowed by Moscow's nearly year-long full-scale war.

Last week, however, authorities fired around a dozen senior officials, including defence officials and a top aide to the president's office.

The moves on Wednesday come as President Zelensky was expected to host a summit with officials from the European Union, which has said corruption reforms are a prerequisite to deeper integration.

Ukraine has been under pressure too from key military and financial backers in European capitals and Washington to make progress on graft to continue receiving arms deliveries.

Investigators from Ukraine's security services, the SBU, released images of a search from the home of Kolomoisky, one of the country's richest men who was barred from entering the United States accusing him of corruption and of undermining democracy.

It said the search had been launched in connection with an investigation into the embezzlement of 40 billion hryvnia (about one billion euros) from two energy companies.

The SBU also said it had uncovered a scheme by the head of the Kyiv tax office over "multimillion-dollar" fraud schemes, accusing the official of abusing a position of authority.