Ukraine's new president Volodymyr Zelensky came under fire Wednesday, just days after taking office, for appointing a chief of staff with links to a controversial oligarch.

But late Tuesday he issued a decree choosing as his top aide Andriy Bogdan, until now a personal lawyer of tycoon Igor Kolomoisky.

During the presidential campaign Zelensky shrugged off accusations that he was running as a front for the interests of Kolomoisky, who owns the television channel that broadcasts the performer's shows.

Authorities accused Kolomoisky of syphoning USD 5.5 billion (4.92 billion euros) from the country's largest bank, PrivatBank, before it was nationalised in 2016.

According to reports, the oligarch returned to Ukraine last week after almost two years of self-imposed exile in Switzerland and Israel.

Critics said Bogdan's appointment was not just politically suspect but also illegal, as he had held government posts under the ousted pro-Russian former president Viktor Yanukovych.

Those who served under Yanukovych are now banned by law from taking certain top positions.

"Zelensky violated the law," MP Yegor Sobolev, one of the authors of the legislation, wrote on Facebook.

The president "puts himself above the law and shows the whole country his true attitude to the rule of law," said Tetyana Kozachenko, who was also behind the legislation.

US special envoy for Ukraine Kurt Volker "strongly recommended not to appoint Bogdan" in telephone talks with Zelensky, local media reported.

Bogdan however told Ukrainian television that claims he was breaking the law were "unfair" and that he had the right to serve in the new administration.

Zelensky, 41, became Ukraine's youngest post-Soviet president after beating incumbent Petro Poroshenko in an April vote.

On Tuesday, he decided to dissolve the current parliament and called early elections for July 21, in a controversial move aimed at cementing his power.

According to the latest opinion polls, Zelensky's newly formed Servant of the People party, named after a sitcom in which he played the role of president, is leading with 44 percent support.

In another controversial staffing decision Wednesday, Zelensky appointed Ivan Bakanov, leader of Servant of the People, to a key role in the security service.

Bakanov has no security experience but is a childhood friend of the president.

Bakanov also worked as a lawyer for Zelensky's production company "Kvartal 95" and was his campaign manager during the race.

(This story has not been edited by Business Standard staff and is auto-generated from a syndicated feed.)