Russian troops take control of key city of Kherson - mayor

Russian forces have seized control of a key port city in southern Ukraine, the city's mayor says. Kherson is the first major city to be taken by Russia, after heavy fighting, since it invaded a week ago. Its mayor, Igor Kolykhaev, said Russian troops had forced their way into the city council building and imposed a curfew on residents.

Several cities have come under intense shelling in one of the most destructive days of the invasion so far. An investigation into possible war crimes and crimes against humanity committed in Ukraine has been launched by the International Criminal Court (ICC) in The Hague.

Russia has for the first time admitted taking heavy military casualties during its attack on Ukraine, with 498 troops killed and a further 1,597 injured. Ukraine says Russia's losses run into the thousands.

Ukraine reports that more than 2,000 civilians have died since the invasion began last Thursday. The conflict has also caused 870,000 people to flee Ukraine - at a rate the UN said would make it the worst refugee crisis this century.

In a Facebook post, Mr Kolykhaev said Russian forces were in control of Kherson, a port on Ukraine's southern Black Sea coast with a population of more than 280,000 people. He urged Russian soldiers not to shoot at civilians, saying there were no Ukrainian forces in the city.

Mr Kolykhaev called on residents to follow conditions set by Russian forces in order to "keep the Ukrainian flag flying". These include: The capture of Kherson came as Russian forces bombarded frontline cities on Tuesday.

In the east, Ukraine's second-largest city, Kharkiv, came under a fierce aerial assault. Its mayor told the BBC shelling and cruise missile strikes were hitting residential areas and inflicting heavy civilian casualties.

Watch: Hussain is in Kherson, Ukraine, and says dire food supplies mean he has to fast to be able to feed his child. And in the southern port of Mariupol, hundreds are feared dead following hours of sustained shelling. But Russian efforts to encircle the capital Kyiv have slowed, with one US official saying a huge Russian convoy to the north of the city has barely moved all day.

In other developments:

* Russian billionaire Roman Abramovich says he is selling Chelsea FC

* Netflix has become the latest tech firm to pause its projects in Russia

* Oil prices surged to an eight-year high

Pictures of fighting in Ukraine have prompted international condemnation of Russia, with an overwhelming majority of UN countries calling on Moscow to immediately withdraw its troops. Only five countries voted against the resolution, including Syria and North Korea.