Ukrainian President Volodymyr Zelensky has removed his former chief of staff Andriy Yermak from the National Security Council amid a sprawling corruption investigation that has rocked Kiev.

Yermak is also no longer a member of the Stavka, the high command of Ukraine's armed forces, according to two presidential decrees published on Friday.

Yermak, a long-standing ally of the president, stepped down as Zelensky's chief of staff last week after anti-corruption authorities conducted searches at his premises.

It remains unclear whether the raids are linked to what has been described as the country's biggest corruption affair since the start of the full-scale Russian invasion in February 2022, involving alleged bribes in energy-related procurement.

Yermak also served as Kiev's chief negotiator in talks on ending the war. That position is now held by former defence minister Rustem Umerov.

Yermak had headed the presidential office since February 2020 and was considered the second most powerful man in Ukraine. Observers see his forced departure as a serious blow to Zelensky, who has lost a long-time confidant.