Ukraine introduced the design for a postage stamp that memorializes a now-famous battle cry rallying the country in its fight against the Russian invasion.

A roundup of key developments and the latest in-depth coverage of Russia's invasion of Ukraine.

The pope urged people to take in refugees from Ukraine. More than 2.5 million people have already fled because of the invasion, according to the United Nations.

The former president said he tested positive for COVID-19. He has a scratchy throat "but am feeling fine otherwise." He said he is vaccinated and boosted.