The announcement by Britain, Denmark, the Netherlands and the United States coincided with a meeting in Brussels of the US-led Ukraine Defense Contact Group -- some 50 nations that are supporting Kyiv militarily.

"Working with our international partners we are able to provide vital air defence equipment, which will help Ukraine support offensive operations and protect critical national infrastructure," UK Defence Secretary Ben Wallace said.

The latest supplies will help Kyiv fend off Russia's "brazen missile and drone attacks against Ukrainian cities", the four allies said in a joint statement.

"The initiative will deliver hundreds of short and medium range air defence missiles and associated systems required to protect Ukraine's critical national infrastructure and further ensure the success of counter-offensive operations in coming months," they said.

Delivery of the equipment is underway and should be complete within weeks, the statement said.

The package consists largely of "Soviet-era missiles", it added, without specifying their source.

Ukraine has already been receiving NATO-grade rocketry from its Western allies, including long-range Storm Shadow missiles from Britain.