More than 50 countries gathered on the sidelines of a NATO meeting in Brussels on Wednesday to discuss bolstering Ukraine's air defense, two days after Russian missiles rained on Kyiv and other cities across the country.

The gathering in Brussels is the first big NATO meeting since Russia annexed four occupied Ukrainian regions, began a partial mobilization and issued veiled nuclear threats — moves the Western alliance has classified as a clear escalation of the war that started with Moscow's invasion of Ukraine on Feb. 24.

Two days after Russian air missile strikes killed 19 people in Ukraine and knocked out power supplies across the country, NATO Secretary-General Jens Stoltenberg urged allies to send more air defense systems to Ukraine.