Just last week, Zelenskyy had named Yermak as Ukraine's top negotiator in a vote of confidence despite growing pressure from opposition figures to remove the divisive chief of staff.
Ukraine's capital faced a night of attacks Friday to Saturday, hours after President Volodymyr Zelenskyy removed his powerful chief of staff and top negotiator following a raid on Andriy Yermak's house as part of a sweeping corruption probe.
Yermak's removal dealt a serious blow to Zelenskyy, who faces a mounting Russian offensive in the east as Washington peddles a plan to end the war that Kiev fears will hand big concessions to Moscow.
Ukrainian negotiators are expected in the United States this weekend for talks on the US plan to end the war.
Yermak, 54, was supposed to have negotiated on behalf of Ukraine at the talks and Zelenskyy said he would hold consultations Saturday over a replacement for him.
Russian drones struck Kiev, killing one person and causing damage and massive power cuts in the capital, city officials said.
Around a dozen people were wounded, as residential buildings were hit in several districts, city officials said.
Explosions were heard through the night and the air alert lasted over nine hours.
"The western part of the capital is without electricity. Power workers will be working to restore supply," Kiev Mayor Vitaly Klitschko said on Telegram.
Leading the talks this weekend is now Ukrainian security council secretary Rustem Umerov, according to two senior Ukrainian officials, who asked to remain anonymous due to the sensitivity of the matter.
But on Friday, Zelenskyy announced in a video address: "The Office of the President of Ukraine will be reorganised. The head of the office, Andriy Yermak, has submitted his resignation."
Minutes later, Zelenskyy signed a decree "to dismiss" Yermak.
On Friday, investigators from the National Anti-Corruption Agency (NABU) said it and the Specialised Anti-Corruption Prosecutor's Office had raided Yermak's apartment as part of an investigation.
They did not say what it was about, and Yermak said he was cooperating fully.
Yermak has been accused of involvement in a $100-million kickback scheme in the strategic energy sector, uncovered by investigators earlier this month.