KYIV - Ukrainian President Volodymyr Zelensky will hold an emergency top-level meeting on Friday, where "fundamental decisions" will be taken in the wake of Russian plans to annex four Ukrainian regions, an official said on Thursday.

The Kremlin says President Vladimir Putin will sign documents on Friday proclaiming Moscow's annexation of regions where Russia organised what Kyiv and the West said were sham referendums staged on Russian-held Ukrainian territory.

Zelensky's office said the national security and defence council would meet on Friday.

Oleksiy Danilov, secretary of the council, said "important and I believe fundamental decisions for our country" would be taken at the meeting.

Danilov, who spoke to Ukraine's 1+1 television station, did not give details.

Zelensky has said repeatedly that the so-called referendums were illegal and warned of a robust Ukrainian response.

The National Security and Defence Council includes, among others, the commander-in-chief of the armed forces, the defence, foreign and prime ministers, and the head of the Ukrainian Security Service.

It is tasked with working with the president on developing and coordinating national security policy. REUTERS