An investigation into possible war crimes in Ukraine has been launched, after Russia was accused of bombing civilians.
The International Criminal Court (ICC) chief prosecutor said evidence was being collected on alleged war crimes, crimes against humanity and genocide.
It came after 38 nations grouped together to refer the situation in Ukraine to the prosecutor's office.
Cities including Kyiv, Kharkiv and Kherson have come under heavy shelling.
Ukraine's President Volodymyr Zelensky has already accused Moscow of war crimes, after it launched air strikes on the country's second city of Kharkiv, killing civilians.
On Wednesday, the mayor of Kherson said Russian forces had seized control of the key port - the first major city to be taken by Moscow since it invaded a week ago.
Earlier this week, the ICC's chief prosecutor Karim Khan said he planned to open an investigation into events in Ukraine "as rapidly as possible" but the referral from 38 nations - including the UK, France and Germany - allowed it to be launched without the need for judicial approval.
He will look at past and present allegations of war crimes, crimes against humanity and genocide, and will go as far back as 2013, before Russia's annexation of Crimea the following year.
Ukraine's state emergency service said more than 2,000 civilians had been killed since the Russian invasion began last Thursday, although the figure has not been independently verified.
The United Nations' high commissioner for refugees said some one million people had already fled the country.
On Wednesday, the UN General Assembly voted overwhelmingly to demand an immediate end to the invasion of Ukraine.
Just four countries - Belarus, North Korea, Eritrea and Syria - joined Russia in opposing a motion calling for the withdrawal of all occupying forces, while 35 nations abstained.
General Assembly resolutions are not legally binding but the move further isolates Russia diplomatically.
On Wednesday, the mayor of Kharkiv told the BBC shelling and cruise missile strikes were hitting residential areas and inflicting heavy civilian casualties.
However, Russian efforts to encircle Kyiv have slowed, with one US official saying a huge Russian convoy to the north of the capital had barely moved all day, despite continued aerial bombardment of the city.
On Tuesday, a TV tower in Kyiv was hit, knocking media off air and killing five people. A nearby memorial to victims of the Holocaust was damaged in the same strike.
Meanwhile, in Kharkiv, at least 10 people were killed when an opera house, concert hall and government offices were struck in the city's Freedom Square.