Ukraine's security service said on Wednesday it had searched an office of the "1+1" TV channel over what it said it was an illegal wiretap that nearly led to the resignation of the prime minister.

In January, Prime Minister Oleksiy Honcharuk submitted a letter of resignation after some media published an audio in which he appeared to criticize the president while talking to ministers and central bank officials.

Honcharuk has previously said the recording had been doctored and was made up of different fragments of what had been said at government meetings.

President Volodymyr Zelenskiy has not accepted the resignation and urged law enforcement bodies to determine who was involved in making the recording.

"The Security Service of Ukraine (SBU) conducted a pre-trial investigation into the illegal use of special technical means of obtaining information at the premises of the Cabinet of Ministers of Ukraine," the SBU said in a statement.

It added that its investigators had found that "individuals who periodically visited the office of '1+1' may be involved in the unlawful use of special technical means of obtaining information."

The security service said it suspected undisclosed individuals had edited and distributed the audio recordings.

The TV channel, which is owned by one of Ukraine's most powerful tycoons, Ihor Kolomoisky, with whom Zelenskiy had close business ties, accused the SBU of trying to put pressure on journalists who produce investigative programs.

The SBU denied that, saying "We are talking about an impartial and comprehensive investigation into a criminal case of an illegal wiretap of the head of government."