"The 'Stand Up For Ukraine' campaign has raised €9.1 billion for people fleeing bombs, inside and outside Ukraine, with an additional billion pledged by EBRD (the European Bank for Reconstruction and Development)," von der Leyen said.

The event, convened by the EU and Canadian Prime Minister Justin Trudeau, was to raise money for internally displaced people in Ukraine and refugees from the war-ravaged country, organisers said.

More than 4.4 million refugees have fled Ukraine since the Russian invasion began on 24 February, according to the United Nations.

Most of them have headed to EU countries including neighbouring Poland, which has taken in more than 2.5 million refugees so far.

The event, partnered by the Global Citizen movement battling poverty, comprised a social media rally on Friday and a pledging conference on Saturday.

Artists including Elton John, Alanis Morissette, Billie Eilish, Annie Lennox and Chris Rock joined the campaign alongside global leaders pledging for their countries.

"We are devastated to see the suffering of people in Ukraine as this conflict unfolds," Elton John said on Facebook.

The 75-year-old rock legend called on his fans to "help people whose lives have been turned upside down and leave everything behind for a safer life.

"No one should have to experience this kind of tragedy," John said.

Determination to act

As part of the fundraising efforts, the European Investment Bank (EIB) announced on its website a four-billion euro programme "to support EU Member States hosting Ukrainian war refugees and to develop vital social infrastructure".

EIB President Werner Hoyer said "the horror we are witnessing strengthens our determination to act".

The European Commission alone has pledged a billion euros, of which €600 million will go to Ukrainian authorities and €400 million to "the frontline states that are doing such an outstanding job in helping the refugees that are coming," von der Leyen added.

In a statement, she promised that "more will come.

"The solidarity of countries, companies and people worldwide offers some light in this dark hour," she said.

"And once the bombs have stopped falling, we will help the people of Ukraine rebuild their country. We will continue to Stand up for Ukraine."

The Warsaw conference was also addressed by Ukrainian President Volodymyr Zelensky.

"Ukrainian courage has already united the whole democratic world," he said in a video message, calling on the West to apply more sanctions on Russian banks and stop buying Russian oil.